Glossary

Knowledge that comes from experience and observation. Example: "Water boils at 100 degrees Celsius."

Knowledge that comes before experience -- things you can know just by thinking. Example: "All bachelors are unmarried."

Reasoning to the best explanation. "The grass is wet; it probably rained." Not certain, but the most likely explanation given the evidence.

Also known as: abductive, inference to the best explanation

The view that certain moral principles are universally true regardless of context, culture, or consequences. Some things are always wrong, no matter what.

Also known as: moral absolutism, absolutist

The philosophy that life is inherently meaningless, but we should embrace the absurdity rather than trying to find or create meaning. Associated with Albert Camus.

Also known as: absurdist

Judge each individual action by whether it produces the most good. Every situation is evaluated fresh -- no rules, just consequences.

A fallacy of attacking the person making the argument rather than the argument itself.

The view that perceptual experiences are ways of sensing rather than objects sensed. Instead of "seeing a red thing," you are "sensing redly." Avoids positing mental objects.

Also known as: adverbialist

The branch of philosophy dealing with beauty, art, and taste. What makes something beautiful? Is beauty objective or in the eye of the beholder?

Also known as: aesthetic

The position that we can't know whether God exists or not. Not a belief -- it's about the limits of human knowledge.

Also known as: agnostic

A step-by-step procedure for solving a problem or accomplishing a task. A recipe is an algorithm for cooking. Computer programs are built from algorithms.

Also known as: algorithms, algorithmic

Reasoning by comparison: if two things are similar in some respects, they might be similar in others too. Powerful but can mislead if the comparison breaks down.

Also known as: analogical, argument from analogy

A style of philosophy emphasizing clear, precise arguments and logical analysis. Dominant in English-speaking universities. Values rigor over grand systems.

Also known as: analytic

The view that the unsaved cease to exist rather than suffering eternally. An alternative to eternal conscious torment.

Also known as: annihilation, conditional immortality

Donald Davidson's view that mental events are physical events, but there are no strict laws connecting mental and physical descriptions. The mind is physical, but unpredictable.

The systematic defense of religious beliefs through rational argument. Christian apologetics, for example, argues that faith is reasonable, not blind.

Also known as: apologetic

Describing God by saying what God is NOT rather than what God IS. "God is not limited, not physical, not changeable." Acknowledges that God is beyond human concepts.

Also known as: negative theology, via negativa

Using someone's expertise as the sole reason to accept a claim. Valid when the expert is relevant; a fallacy when they're not (celebrity endorsements of medicine).

Also known as: argument from authority

Arguing that something is good because it's "natural" or bad because it's "unnatural." Arsenic is natural too.

Also known as: naturalistic fallacy

A set of reasons (premises) that support or challenge a statement. Not a fight -- a structured case for or against something.

Also known as: arguments

A visual diagram showing how reasons support or attack a claim. Like a family tree for ideas -- each node is a statement, and the connections show logical relationships.

Also known as: argument mapping

Ancient Greek philosopher (384-322 BCE), student of Plato. Studied everything: logic, biology, ethics, politics. Invented formal logic. Tutor to Alexander the Great.

A branch of Protestant theology emphasizing free will and the belief that humans can choose or reject God's offer of salvation.

Also known as: arminian

The quality of existing independently, needing nothing else for existence. In theology, God's self-existence -- uncaused and uncreated.

The absence of belief in gods, or the active belief that no gods exist. Ranges from "I don't believe" to "I believe there isn't."

Also known as: atheist, atheistic

The idea that a wrong can be made right -- in theology, how humanity's relationship with God is repaired. Different theories explain how this works.

An argument that disagrees with a statement and provides reasons why it might be wrong.

Also known as: attacking, attacks, challenge, challenges

The right and ability to make your own choices and govern yourself. A foundational value in ethics, law, and politics.

Also known as: autonomous

A statement accepted as true without proof, serving as a starting point for reasoning. Example: "Things equal to the same thing are equal to each other."

Also known as: axioms, axiomatic

A method of updating beliefs based on new evidence. You start with a prior probability, get new data, and calculate a revised probability. The foundation of modern statistics and AI.

Also known as: bayesian, bayes' theorem, bayesianism

A fallacy where the conclusion is assumed in one of the premises. The argument goes in a circle.

The view that mental states are nothing more than behavioral dispositions. To be in pain is just to be disposed to cry out and avoid the cause. No inner mental life needed.

Also known as: behaviorist

The ethical principle of doing good and acting in others' best interests. One of the four pillars of medical ethics.

The ethics of biological and medical issues: euthanasia, genetic engineering, abortion, organ donation, animal testing. Where science meets morality.

Also known as: bioethical

A class of problems that can be solved quickly by a computer that's allowed to flip coins (use randomness), with a small chance of being wrong. Essentially: problems solvable efficiently with randomization.

The responsibility to provide evidence for a claim. Generally falls on the person making the claim, not on the person questioning it.

A branch of Protestant theology emphasizing God's sovereignty, predestination, and the idea that salvation is entirely God's work, not earned by humans.

Also known as: calvinist, reformed theology

Kant's test for moral rules: "Act only according to rules you could want everyone to follow." If it can't be universal, it's wrong.

The relationship between cause and effect. When one event brings about another. Philosophers debate what this really means.

Also known as: causal, causality

John Searle's thought experiment: a person in a room follows rules to produce Chinese responses without understanding Chinese. Argues that computers don't truly "understand" -- they just manipulate symbols.

Also known as: chinese room argument

The view of atonement as cosmic victory: Christ defeated the powers of evil (sin, death, the devil) through his death and resurrection.

Using the conclusion as one of the premises. "The Bible is true because God wrote it, and we know God wrote it because the Bible says so."

Also known as: circular argument, petitio principii

A type of statement expressing an opinion or position. Something that can be agreed or disagreed with.

Also known as: claims

The inductive equivalent of a sound argument: the reasoning is strong AND the premises are true. Not guaranteed to be right, but as good as inductive reasoning gets.

Also known as: cogency

A systematic error in thinking that affects everyone. Your brain takes shortcuts that usually work but sometimes lead you astray. Examples: confirmation bias, anchoring, sunk cost fallacy.

Also known as: cognitive biases, bias

The view that beliefs are justified by how well they fit together, like a web. No single belief needs to be "the foundation."

Also known as: coherentist

The view that community and social bonds are more important than pure individual rights. We are shaped by our communities.

Also known as: communitarian

The view that free will and determinism can both be true at the same time. You can make genuine choices even if everything has a cause.

The view that all perceptual experience is shaped by concepts we already have. You can't perceive anything without categorizing it.

Also known as: conceptualist

The main point an argument is trying to prove or disprove. The statement that the premises lead to.

Also known as: conclusions

The view that both God and created things are genuine causes. God doesn't do everything alone, but cooperates with natural causes to bring about effects.

An "if-then" statement. Example: "If it rains, then the ground gets wet." The conclusion depends on a condition being true.

Also known as: conditionals

A score showing how well-supported a statement is, based on the number and quality of arguments for and against it. Higher = more evidence supports it.

Also known as: confidence score

The tendency to search for, interpret, and remember information that confirms what you already believe, while ignoring evidence that contradicts it.

The state of being aware of and able to think about yourself, your surroundings, and your experiences. The "hard problem" is explaining why we have subjective experience at all.

Also known as: conscious

Voluntary, informed agreement. In ethics, a key principle: actions affecting others require their genuine agreement.

Also known as: informed consent

The ethical view that the morality of an action depends entirely on its outcomes. If the results are good, the action is good.

Also known as: consequentialist

A political philosophy emphasizing tradition, social stability, and gradual change rather than radical reform.

Also known as: conservative

The view that knowledge and meaning are constructed by humans through experience and social interaction, not discovered as fixed truths.

Also known as: constructivist, social constructivism

A broad tradition including existentialism, phenomenology, and critical theory. Tends to focus on lived experience, history, and culture rather than formal logic.

Also known as: continental

Something that happens to be true but could have been otherwise. The opposite of necessity -- things that depend on circumstances.

Also known as: contingent

Something that could have been otherwise. Your existence is contingent -- you might not have been born. Contrast with "necessary," which couldn't have been otherwise.

Also known as: contingency

A statement that is necessarily false because it asserts two incompatible things. "It is raining and it is not raining" (at the same time, in the same place).

Also known as: contradictory, self-contradictory

An argument for God's existence based on the fact that the universe exists. "Everything has a cause, so the universe must have a first cause."

Also known as: cosmological

The view that all human beings belong to a single global community. Borders are morally arbitrary -- you have obligations to people everywhere, not just your country.

Also known as: cosmopolitan

A "what if" statement about something that didn't happen. "If I had studied more, I would have passed." Used in philosophy to analyze causation and free will.

Also known as: counterfactuals, counterfactual reasoning

The percentage of statements in a topic that have at least one argument. Higher coverage means more statements have been debated.

Scottish philosopher (1711-1776) who argued that all knowledge comes from experience. Famously skeptical about causation, miracles, and the existence of the self.

Also known as: Hume, Humean

About what is said. "The president must be over 35" is de dicto -- it's about the description "president," not about any particular person.

About the thing itself. "The president (whoever that is) could have been someone else" is de re -- it's about the office, not the specific person.

Whether a problem can be solved by any algorithm at all, given enough time. Some problems are "undecidable" -- no computer can ever solve them, no matter how long it runs.

Also known as: decidable, undecidable

Reasoning from general principles to specific conclusions. "All humans are mortal. Socrates is human. Therefore, Socrates is mortal." If the premises are true, the conclusion must be.

Also known as: deductive, deductive reasoning

A philosopher, scholar, or thinker whose arguments are represented in the database. Their historical positions are mapped to modern debate.

Also known as: defenders

The belief that God created the universe but doesn't intervene in it -- like a watchmaker who built the clock and let it run.

Also known as: deist, deistic

The question of what makes something science vs. non-science. Is astrology science? What about string theory? There's no universally accepted boundary.

An ethical theory focused on rules and duties rather than outcomes. Some actions are right or wrong regardless of their consequences.

Also known as: deontological

About how things actually are, not how they should be. Science is descriptive; ethics is normative.

The view that every event, including human decisions, is the inevitable result of prior causes. The opposite of free will in some frameworks.

A system where the current state fully determines all future states. Given the same starting conditions, the same thing always happens. Classical physics is deterministic; quantum mechanics is not.

Also known as: deterministic system

A method of reasoning through opposing ideas: thesis, antithesis, synthesis. You arrive at truth by working through contradictions, not avoiding them.

Also known as: dialectical

The inherent worth of every person that demands respect, regardless of their status, abilities, or circumstances.

Also known as: human dignity

A situation where you must choose between two options, both of which have undesirable consequences. In logic, a formal argument structure with two conditional premises.

Also known as: dilemmas

The view that we perceive the world directly, as it really is, rather than through mental representations. What you see is what's there.

Also known as: naive realism

A theory of perception arguing that genuine perception and hallucination are fundamentally different kinds of mental events, not variations of the same thing.

Also known as: disjunctivist

The question of how society should distribute resources. Should everyone get equal shares? Should the hardest workers get more? Should the most needy get priority?

The doctrine that God has no parts -- God's attributes (love, justice, power) are all identical to God's being. God doesn't have goodness; God is goodness.

Also known as: DDS

The view that mind and body are fundamentally different kinds of things. Your thoughts are not the same as your brain.

Also known as: dualist

The aspects of consciousness we can explain with neuroscience: how the brain processes information, controls behavior, and reports on mental states. "Easy" doesn't mean simple -- just that we know how to approach them.

Also known as: easy problems

The traditional doctrine that the unsaved suffer conscious punishment forever. One of several views on the afterlife debated in theology.

The view that all people are fundamentally equal and deserve equal rights and opportunities. Debates arise about what kind of equality matters most.

Also known as: egalitarian

The radical view that everyday mental concepts like "beliefs" and "desires" are fundamentally wrong and will be replaced by neuroscience. Folk psychology is just bad science.

Also known as: eliminative materialism, eliminativist

When complex systems display properties that their individual parts don't have. Consciousness might "emerge" from neurons the way wetness "emerges" from H2O molecules.

Also known as: emergent, emergentism

A property of a complex system that none of its individual parts possess. Individual neurons aren't conscious, but a brain made of neurons is. Wetness emerges from H2O molecules.

Also known as: emergence

Based on observation and evidence from the real world, rather than pure theory. "The data shows..." is an empirical claim.

The view that knowledge comes primarily from sensory experience and evidence, rather than pure reasoning.

Also known as: empirical, empiricist

A measure of disorder or randomness. In physics: energy that can't do useful work. In information theory: the amount of uncertainty or surprise in a message.

The view that mental events are caused by physical events in the brain, but mental events themselves have no effect on the physical world. Your thoughts are like steam from a train -- produced by the engine but not driving it.

Also known as: epiphenomenal, epiphenomenon

When someone's knowledge or testimony is unfairly dismissed because of prejudice. Being disbelieved because of your race, gender, or social status.

Good thinking habits: open-mindedness, intellectual humility, honesty, courage to question your own beliefs. The character traits of a good reasoner.

Also known as: epistemic virtues

The study of knowledge: what counts as knowledge, how we know things, and the limits of what we can know.

Also known as: epistemological

Using the same word with different meanings in the same argument. "A bank is by the river. Banks hold money. Therefore, money is by the river."

The view that all moral statements are false because there are no moral facts. We sincerely believe murder is wrong, but we're all mistaken -- there's nothing "out there" making it wrong.

Also known as: moral error theory

The study of "last things" -- death, judgment, heaven, hell, and the end of the world. What happens after we die?

Also known as: eschatological

The core properties that make something what it is. A triangle's essence is having three sides. But do humans have an essence? Existentialists say no.

Also known as: essential

The view that past, present, and future all exist equally -- like a timeline where every moment is real. The passage of time is an illusion of perspective.

Also known as: eternalist, block universe

An ancient Greek concept meaning "human flourishing" or "the good life." Not just happiness, but living well and doing well.

The argument that while some evil might be justified, the sheer amount and intensity of suffering in the world makes God's existence unlikely (not impossible, just improbable).

Careful, detailed interpretation of a text (usually scripture), drawing out the original meaning rather than reading modern ideas into it.

Also known as: exegetical

A philosophy emphasizing individual existence, freedom, and choice. You define your own meaning through your actions.

Also known as: existentialist, existential

The view that moral statements don't describe facts -- they express attitudes. "Murder is wrong" means something like "Boo, murder!" Not a factual claim, but an emotional expression.

Also known as: expressivist

The set of things a term applies to. The extension of "dog" is all dogs. Contrasts with intension (the meaning or definition).

The view that what makes a belief justified can include factors the person isn't aware of. Your belief can be justified by reliable processes even if you can't explain why.

Also known as: externalist, epistemic externalism

A type of statement based on empirical evidence or widely accepted data. Can still be debated, but is grounded in evidence.

Also known as: facts

A flaw in reasoning that makes an argument invalid. Example: "Everyone believes it, so it must be true" (appeal to popularity).

Also known as: fallacies, logical fallacy

Presenting only two options when more exist. "You're either with us or against us." Reality usually has more than two possibilities.

Also known as: false dilemma, black and white thinking

Presenting only two options when more exist. "You're either with us or against us" ignores the possibility of being neutral or partially agreeing.

Also known as: false dichotomy, black-and-white thinking

Karl Popper's criterion: a theory is scientific only if it could potentially be proven wrong by evidence. "All swans are white" is falsifiable (find a black swan). Unfalsifiable claims aren't scientific.

Also known as: falsifiable, falsification

The view that faith is independent of reason -- you believe not because of evidence, but because of trust or commitment.

Also known as: fideist

Knowledge of events before they happen. In theology, the question of whether God's foreknowledge is compatible with human free will.

Also known as: divine foreknowledge

The study of reasoning using precise symbolic languages. Translates arguments into formulas to check if they're valid. Think of it as math for reasoning.

The idea that knowledge is built on basic, self-evident truths -- like a building needs a solid foundation before you can build up.

Also known as: foundationalist

The ability to make choices that are genuinely your own, not predetermined by prior causes. One of the most debated questions in philosophy.

The response to the problem of evil arguing that God allows evil because genuine free will requires the possibility of choosing wrongly. A world with free will is better than one without it.

German philosopher (1844-1900) who declared "God is dead" and challenged traditional morality. Advocated creating your own values. Often misunderstood and misquoted.

Also known as: Nietzsche, Nietzschean

The theory that mental states are defined by what they do, not what they're made of. Pain is anything that plays the role of pain, whether in a brain or a computer.

Also known as: functionalist

Aristotle's idea that virtue is a balance between two extremes. Courage is the mean between cowardice and recklessness. Generosity between stinginess and wastefulness.

Evil or suffering that serves no purpose -- not necessary for free will, soul-making, or any greater good. If gratuitous evil exists, it's hard to explain why God allows it.

A perceptual experience with no corresponding object in reality. You see something that isn't there. Raises deep questions about the nature of perception.

The famous proof that no computer program can predict whether every other program will eventually stop or run forever. A fundamental limit of computation.

The view that every event is caused by prior events, including human decisions -- and therefore free will is an illusion.

Also known as: hard determinist

David Chalmers' term for the difficulty of explaining why physical processes in the brain give rise to subjective experience. Why does it feel like something to see red?

Also known as: hard problem

The view that pleasure is the highest good and the proper aim of life. Ranges from physical pleasure to deep contentment.

Also known as: hedonist, hedonistic

The art and science of interpretation, especially of texts. How should we read and understand ancient or complex writings?

Also known as: hermeneutical, hermeneutic

A mental shortcut or rule of thumb that usually works but isn't guaranteed. "If it looks like a duck and quacks like a duck..." is a heuristic.

Also known as: heuristics

The opposite of reductionism: the whole is more than the sum of its parts. You can't understand consciousness by studying individual neurons alone.

Also known as: holistic

The philosophical view that reality is fundamentally mental or idea-based. The physical world depends on mind or consciousness, not the other way around.

Also known as: idealist, absolute idealism

The view that mental states are identical to brain states. Pain literally IS a certain pattern of neuron firing, not just correlated with it.

Also known as: mind-brain identity

A perception that misrepresents some feature of reality. The stick looks bent in water, but it isn't. Different from hallucination, where there's nothing there at all.

Also known as: perceptual illusion

Being present within the world. God's immanence means being actively involved in creation, not distant.

Also known as: immanent

German philosopher (1724-1804) who revolutionized ethics and epistemology. Argued that moral rules must be universal, and that our minds actively shape our experience of reality.

Also known as: Kant, Kantian

The quality of being unchangeable. In theology, the idea that God's nature, character, and promises never change.

Also known as: immutable

The belief that God became human -- specifically, that Jesus Christ was God in human form. Central to Christian theology.

Thomas Kuhn's idea that competing scientific theories can be so different that they can't be directly compared. Newtonian and Einsteinian physics use "mass" differently.

Also known as: incommensurable

A word whose reference changes depending on who says it and when. "I", "here", "now", and "this" are indexicals. Their meaning is fixed, but their reference shifts with context.

Also known as: indexicals, indexicality

Reasoning from specific observations to general conclusions. "Every swan I've seen is white, so all swans are probably white." (Spoiler: not all swans are white.)

Also known as: inductive, inductive reasoning

The process of drawing a conclusion from evidence or premises. When you see dark clouds and grab an umbrella, you made an inference.

Also known as: infer, inferences

A chain of reasoning that goes back forever with no end point. "What caused the cause of the cause?" If every explanation needs its own explanation, you get an infinite regress.

Refusal to obey authority. In theology, the question of whether disobeying God can ever be justified.

A profile of which thinkers and topics align with your contributions. Shows whose philosophical style you most resemble.

The meaning or concept behind a term, as opposed to the things it applies to. The intension of "bachelor" is "unmarried adult male." The extension is the set of all actual bachelors.

Also known as: intensional

The property of mental states being "about" or "directed at" something. Your thought about pizza is about pizza. Rocks don't have intentionality; minds do.

Also known as: intentional

The view that what makes a belief justified must be accessible to the person holding the belief. You need to know why you believe what you believe.

Also known as: internalist, epistemic internalism

Daniel Dennett's term for a thought experiment designed to trigger a specific intuition. Like leading questions for your philosophical instincts.

Also known as: intuition pumps

A thought experiment: what if your experience of red is what I experience as green, but we both call it "red"? We'd never know. Raises questions about whether subjective experience can be studied objectively.

Swiss-French philosopher (1712-1778) who believed humans are naturally good but corrupted by society. "Man is born free, and everywhere he is in chains."

Also known as: Rousseau

English philosopher (1632-1704) who argued the mind starts as a "blank slate." Influenced democratic theory -- government must have the consent of the governed.

Also known as: Locke, Lockean

American philosopher (1921-2002) who asked: what principles of justice would you choose if you didn't know your place in society? His "veil of ignorance" thought experiment is hugely influential.

Also known as: Rawls, Rawlsian

English philosopher (1806-1873) who refined utilitarianism and championed individual liberty. Argued for free speech, women's rights, and "the greatest happiness" principle.

Also known as: Mill

The classical definition of knowledge: you know something when (1) it's true, (2) you believe it, and (3) you have good reasons to believe it.

Also known as: JTB

German philosopher (1818-1883) who analyzed how economic systems shape society. Argued that capitalism exploits workers and would eventually be replaced. His ideas reshaped the world.

Also known as: Marx, Marxist, Marxism

A political philosophy emphasizing individual rights, freedom, consent of the governed, and equality before the law.

Also known as: liberal, classical liberalism

The view that humans have genuine freedom to choose differently than they do, not determined by prior causes.

A political philosophy that maximizes individual liberty and minimizes government intervention in both personal and economic matters.

Also known as: libertarian

The stronger argument that the existence of any evil is logically incompatible with an all-powerful, all-knowing, all-good God. If God exists, evil can't. But evil does.

Austrian-British philosopher (1889-1951) who wrote two revolutionary books that contradicted each other. Early work: language mirrors reality. Later work: meaning comes from use.

Also known as: Wittgenstein

A doctrine of military strategy where full-scale use of nuclear weapons by two opposing sides would cause the complete annihilation of both.

The view that everything that exists is physical matter. Mental states are ultimately brain states.

Also known as: materialist, physicalism

The study of parts and wholes. When does a collection of parts form a genuine whole? Is a pile of sand a single thing? What about your body?

Also known as: mereological

A system where success is based on ability and effort rather than wealth, social class, or connections. Debated whether true meritocracy is achievable or desirable.

Also known as: meritocratic

The branch of philosophy dealing with the fundamental nature of reality, existence, time, and causation.

Also known as: metaphysical

A type of logic dealing with possibility and necessity. "It's possible that..." and "It must be that..." are modal claims.

The study of possibility and necessity. "Could things have been different?" Modal claims use words like "must," "might," "could," "necessarily."

Also known as: modal

A basic rule of logic: If A implies B, and A is true, then B must be true. Example: If it rains, the ground is wet. It rained. Therefore, the ground is wet.

A rule of logic: If A implies B, and B is false, then A must be false. Example: If it rained, the ground would be wet. The ground is dry. Therefore, it didn't rain.

The view that God knows not only what will happen, but what would happen in every possible scenario. God uses this "middle knowledge" to sovereignly guide events while preserving free will.

Also known as: molinist, middle knowledge

The view that everything is made of one fundamental kind of stuff. Whether that stuff is physical (materialism) or mental (idealism), there's only one kind.

Also known as: monist

The capacity to make moral judgments and be held responsible for your actions. What makes someone a moral agent.

Also known as: moral agent

The view that there are no objective moral facts. Moral claims are expressions of attitude, social convention, or personal preference -- not discoveries about reality.

Also known as: moral anti-realist

A situation where every available option involves some moral wrong. You're forced to choose the "least bad" option. No clean hands possible.

Also known as: moral dilemmas

The view that Christ's death primarily works by moving us to love God in return. Salvation comes through being inspired by the example of divine love.

An immediate, gut-level moral judgment that doesn't come from explicit reasoning. "That's just wrong!" Debated whether these are reliable guides to morality.

Also known as: moral intuitions, intuitionism

The uncomfortable fact that luck affects moral judgments. Two equally reckless drivers -- one hits a pedestrian, the other doesn't. We judge them differently even though their choices were the same.

The view that moral facts are natural facts. "Good" can be defined in terms of things like wellbeing, flourishing, or evolutionary fitness. Morality is part of the natural world.

Also known as: moral naturalist

The view that moral facts exist independently of what anyone thinks. Some things really are right or wrong, not just opinions.

Also known as: moral realist

The view that moral judgments are not universally true but depend on culture, society, or individual perspective.

Also known as: relativism, moral relativist

The idea that the same mental state can be produced by different physical systems. Pain might be one thing in a human brain and something different in an octopus brain, but it's still pain.

Also known as: multiply realizable

The commonsense view that we perceive the world directly as it actually is. What you see is what's really there. Challenged by illusions and hallucinations.

Also known as: naive realism, common sense realism

The idea that moral principles are built into the nature of reality and can be discovered through reason, not just invented by humans.

The process where organisms with traits better suited to their environment tend to survive and reproduce more. The main mechanism of evolution.

Also known as: survival of the fittest

The attempt to learn about God through reason and observation of the natural world, rather than through revelation or scripture.

Something that must be the case and couldn't have been otherwise. "2+2=4" is necessary. "The sky is blue" is contingent -- it could have been different.

Also known as: necessity

A being that must exist and cannot not exist. In theology, God is argued to be the one necessary being, while everything else is contingent.

Something that must be true and could not possibly be otherwise. "2 + 2 = 4" is necessary; "it's raining" is contingent.

Also known as: necessary, necessarily

Freedom FROM interference. Nobody stopping you from speaking, traveling, or practicing your religion. Contrast with positive liberty -- having the means to do so.

Rights that require others to NOT do something to you. Freedom of speech means the government can't silence you. You have a right to not be harmed.

The scientific study of the brain and nervous system. Relevant to philosophy because it raises questions about consciousness, free will, and the nature of the mind.

Also known as: neuroscientific

The view that life lacks objective meaning, purpose, or intrinsic value. Often misunderstood as being depressing -- many nihilists find it liberating.

Also known as: nihilist, nihilistic

The view that abstract objects (like numbers, properties, and universals) don't really exist. Only particular, concrete things are real. "Redness" doesn't exist; only red things do.

Also known as: nominalist

Latin for "it does not follow." A conclusion that has no logical connection to the premises. "It's sunny, therefore the economy will improve."

The idea that some of what we perceive doesn't require concepts or language to represent. You can see a shade of color without having a word for it.

"First, do no harm." The ethical principle of avoiding actions that cause unnecessary suffering or damage.

Also known as: nonmaleficence

About how things should be, not how they are. "People should be kind" is normative. "People are sometimes kind" is descriptive.

Also known as: normative ethics

Problems where a solution can be checked quickly, even if finding the solution might take a long time. The famous "P vs NP" question asks: if you can check an answer quickly, can you also find it quickly?

Also known as: NP-complete, NP-hard

The principle that the simplest explanation is usually the best one. Don't multiply causes beyond what's necessary.

Also known as: occams razor, ockham's razor

The view that God is the only true cause of everything. What looks like causation (a ball hitting another) is really God creating each event. Associated with Malebranche.

Also known as: occasionalist

The quality of being all-powerful. The ability to do anything that is logically possible.

Also known as: omnipotent

The quality of knowing everything. In theology, God's complete knowledge of all things -- past, present, and future.

Also known as: omniscient

An argument for God's existence based purely on logic and the definition of God. If God is "the greatest conceivable being," then God must exist.

The study of what exists and the nature of being. Questions like "What is real?" and "What kinds of things exist?"

Also known as: ontological

The view that God doesn't know the future exhaustively because free choices haven't been made yet. God knows all possibilities but the future is genuinely open.

Also known as: open theist

The doctrine that all humans inherit a sinful nature from Adam and Eve's disobedience in the Garden of Eden.

In computer science, the class of problems that can be solved quickly (in a reasonable amount of time). "P" stands for polynomial time -- as the problem gets bigger, the time to solve it grows at a manageable rate.

Also known as: complexity class P

The view that God includes and penetrates the entire universe, but is also greater than the universe. The world is "in" God, but God is more than the world.

Also known as: panentheist

The view that consciousness is a fundamental feature of all matter. Even simple particles have some basic form of experience. Not as crazy as it sounds -- it solves the "hard problem" of consciousness.

Also known as: panpsychist

The belief that God and the universe are one and the same. Everything is God, and God is everything.

Also known as: pantheist, pantheistic

Thomas Kuhn's term for a shared framework of assumptions, methods, and questions that scientists work within. When paradigms shift (like Newton to Einstein), everything changes.

Also known as: paradigm shift

Thomas Kuhn's idea that science doesn't just accumulate knowledge gradually -- it undergoes revolutions where the entire framework changes. Example: from Newtonian physics to Einstein's relativity.

Also known as: paradigm

A statement or situation that seems contradictory or absurd but may actually be true, or reveals a deep problem in our thinking. "This sentence is false" is a classic paradox.

Also known as: paradoxes, paradoxical

Blaise Pascal's argument that it's rational to believe in God because: if God exists, you gain everything; if not, you lose nothing.

Also known as: pascals wager

Limiting someone's freedom "for their own good." Like seatbelt laws or banning dangerous drugs. The question: when is it justified to override someone's choices?

Also known as: paternalist, paternalistic

A theory of atonement where Christ takes the punishment that humanity deserves, satisfying divine justice on our behalf.

Also known as: penal substitutionary

What your senses represent to you about the world. The "information" in what you see, hear, or feel. Debated whether it's conceptual or non-conceptual.

Also known as: scenario-content

What it's like to see, hear, taste, touch, or smell something. The subjective aspect of perceiving the world around you.

What makes you "you" over time? If every cell in your body is replaced, are you the same person? The philosophy of what continuity of self really means.

The study of conscious experience from the first-person perspective. How things appear to us, rather than what they "really" are.

Also known as: phenomenological

A hypothetical being that behaves exactly like a human but has no inner experience. No qualia, no consciousness -- just an automaton that acts conscious. If conceivable, consciousness must be non-physical.

Also known as: p-zombie, philosophical zombies

How does language relate to reality? What do words mean, and how do they get their meaning? Can language capture truth?

The view that everything that exists is physical. There is nothing "over and above" the physical world -- consciousness included.

Also known as: physicalist

Ancient Greek philosopher (428-348 BCE), student of Socrates. Believed in a realm of perfect "Forms" behind physical reality. Founded the Academy. Wrote dialogues featuring Socrates.

The view that abstract objects (numbers, forms, properties) exist in a non-physical realm. The number 7 exists whether or not anyone thinks about it. Named after Plato.

Also known as: platonist, mathematical platonism

Has two meanings: (1) In voting theory, voting for only one candidate when you could vote for several. (2) In meta-ethics, choosing without rational reasons when values can't be compared -- making a decision even when there's no basis to prefer one option over another.

Freedom TO do something -- having the resources and opportunities to live a good life. Having healthcare, education, and economic security. Contrast with negative liberty.

Rights that require others to DO something for you. The right to education means someone must provide schools. More controversial than negative rights.

A complete way things could have been. "A world where dinosaurs never went extinct" is a possible world. Philosophers use them to think about what's possible vs. necessary.

Also known as: possible worlds

A way of thinking about what could have been different. "In some possible world, dinosaurs never went extinct." Used to analyze necessity and possibility.

A broad intellectual movement skeptical of universal truths, grand narratives, and objective knowledge. Emphasizes interpretation, context, and power.

Also known as: postmodern, postmodernist

The study of how context contributes to meaning. "Can you pass the salt?" is literally a yes/no question, but pragmatically it's a request.

Also known as: pragmatic

A philosophical approach that judges ideas by their practical consequences. An idea is "true" if it works in practice.

Also known as: pragmatist, pragmatic

The belief that God has already decided who will be saved and who won't, before they are even born.

Also known as: predestined

A more powerful form of logic that looks inside sentences at subjects, predicates, and quantifiers ("all," "some"). Can express "All dogs are mammals" formally.

Also known as: first-order logic

A supporting reason within an argument. Each premise is a statement that helps make the case.

Also known as: premises

The view that only the present moment exists. The past is gone and the future hasn't happened yet. Contrasts with eternalism.

Also known as: presentist

A hidden assumption that must be true for a statement or question to make sense. "Have you stopped cheating?" presupposes that you were cheating.

Also known as: presuppose, presuppositions

The challenge of explaining why evil exists if God is all-powerful, all-knowing, and all-good. One of the oldest and most debated questions in philosophy.

The view that the brain has both physical properties and mental properties that can't be reduced to the physical. Softer than substance dualism.

The act of appeasing or satisfying God's wrath. In theology, the idea that a sacrifice turns away divine anger.

A clear statement that can be argued for or against. Think of it as a claim or idea that people can debate.

Also known as: propositions

The simplest form of formal logic, dealing with whole sentences connected by "and," "or," "not," and "if...then." Doesn't look inside sentences, just at how they connect.

Also known as: sentential logic

The subjective, conscious experiences of the world -- what it feels like to see red, taste coffee, or feel pain. The "what it's like" of experience.

The physics of the very small -- atoms and subatomic particles. Famous for counterintuitive results: particles can be in two states at once, observation affects outcomes.

Also known as: quantum physics, quantum theory

An early view of atonement: Christ's death was a ransom paid to free humanity from the devil's power. One of the oldest interpretations of how salvation works.

The view that knowledge comes primarily from reason and logic, not just from sensory experience.

Also known as: rationalist

John Rawls' theory: design society as if you didn't know what position you'd hold in it (the "veil of ignorance"). Leads to protecting the worst-off.

Also known as: veil of ignorance, original position

The view that things exist independently of our minds. There's a real world out there whether or not anyone is looking at it.

Also known as: realist, philosophical realism

A distraction that diverts attention from the real issue. Bringing up an irrelevant topic to avoid addressing the actual argument.

A method of proof: assume the opposite of what you want to prove, show it leads to a contradiction, and conclude your original claim must be true.

Also known as: reductio, proof by contradiction

Explaining something complex in terms of simpler parts. "Water is just H2O molecules." The question is whether everything can be reduced this way -- can consciousness be reduced to brain activity?

Also known as: reductive

The view that complex things can be fully explained by their simpler parts. The mind is "just" brain activity; society is "just" individuals.

Also known as: reductionist, reduce

The relationship between a word or expression and the thing in the world it picks out. "The Eiffel Tower" refers to a specific structure in Paris.

The view that truth, morality, or knowledge is not absolute but depends on the perspective, culture, or context. What's "right" varies from place to place.

Also known as: relativist, cultural relativism

The view that a belief counts as knowledge if it was produced by a reliable process -- like vision, memory, or good reasoning. You don't need to prove the process works; it just needs to work.

Also known as: reliabilist

A personal experience that the individual interprets as an encounter with the divine. Debated whether these count as evidence for God's existence.

French philosopher (1596-1650) who said "I think, therefore I am." Radical skeptic who doubted everything except the fact of his own thinking. Father of modern philosophy.

Also known as: Descartes, Cartesian

The discovery that many published scientific studies can't be reproduced by other researchers. Raises questions about how reliable published research really is.

The view that the mind relates to the world through internal representations. We don't see the world directly -- we see our brain's picture of it.

Also known as: representationalist, indirect realism

An approach focused on repairing harm rather than punishing offenders. Brings together victims, offenders, and community.

Also known as: restorative

The idea that punishment should be proportional to the crime -- wrongdoers deserve to suffer consequences for their actions.

Also known as: retribution, retributive, retributivism

Knowledge that comes directly from God, not from human reasoning. The Bible, Quran, and other sacred texts are considered revelation by their respective faiths.

Saul Kripke's term for a name or expression that refers to the same thing in every possible world. "Water" rigidly designates H2O -- even if we'd never discovered its chemical composition.

Also known as: rigid designation

Follow rules that generally produce the most good, even if breaking the rule would produce more good in a specific case. "Don't lie" as a rule produces better outcomes overall.

The principle that human life has inherent, inviolable value simply because it exists -- not because of what it can do.

Relating to meaning. Semantic questions ask what words and sentences mean, as opposed to syntactic questions (about grammar) or pragmatic questions (about context and use).

Also known as: semantics

The meaning or mode of presentation of an expression, as opposed to what it refers to. "The Morning Star" and "The Evening Star" have different senses but the same reference (Venus).

Also known as: fregean sense

The raw subjective experiences that seem to come from our senses -- colors, sounds, textures. The question is whether these are mental representations or direct contact with reality.

Also known as: sense datum, sensory data

If you replace every plank of a ship one by one, is it still the same ship? What about the original planks reassembled? A puzzle about identity and change that's 2,500 years old.

French existentialist philosopher (1908-1986) who wrote "The Second Sex." Argued that women are made, not born -- society constructs gender roles. Pioneer of feminist philosophy.

Also known as: de Beauvoir, Beauvoir

The practice of questioning claims and withholding judgment until sufficient evidence is available. Healthy doubt as a method.

Also known as: skeptic, scepticism, sceptic

The fallacy of arguing that one small step will inevitably lead to extreme consequences, without showing why each step necessarily follows.

The idea that people agree (explicitly or implicitly) to give up some freedoms in exchange for social order and protection.

Also known as: social contract theory

Ancient Greek philosopher (470-399 BCE) who taught by asking questions. Never wrote anything down. Executed for "corrupting the youth." The Socratic method -- learning through questioning -- is his legacy.

Another name for compatibilism: determinism is true, but free will is still possible because "free" just means "not coerced."

Also known as: soft determinist

The extreme philosophical position that only your own mind is certain to exist. Everything else might be an illusion.

Also known as: solipsist

The study of salvation -- how humans are saved or redeemed, and what that means across different religious traditions.

Also known as: soteriological

John Hick's argument that suffering exists to help humans develop virtues like courage, compassion, and patience. Earth is a "soul-making" environment, not paradise.

Also known as: soul making

An argument that is both valid (the logic works) AND has true premises. A sound argument guarantees a true conclusion. The gold standard of reasoning.

Also known as: soundness

An argument is sound when it is both valid (correctly structured) AND has true premises. The gold standard of good arguments.

Also known as: sound

Supreme authority over a territory or domain. In theology, God's sovereignty means ultimate control over everything that happens.

Also known as: sovereign

Presenting the strongest possible version of an opponent's argument, even stronger than they stated it. The opposite of strawmanning. Shows intellectual honesty.

Also known as: steelman

Involving randomness or probability. A stochastic system has some inherent unpredictability. Weather is stochastic -- you can predict trends but not exact outcomes.

An ancient philosophy teaching that we can't control external events, only our responses to them. Focus on what you can control; accept what you can't.

Also known as: stoic, stoics

A fallacy where someone misrepresents an opponent's argument to make it easier to attack.

Also known as: strawman

Misrepresenting someone's argument to make it easier to attack. You knock down a "straw man" instead of engaging with what they actually said.

Also known as: strawman, straw man

In philosophy, the fundamental "stuff" that things are made of. What exists independently and underlies all properties.

The view that mind and body are two completely different kinds of substance -- one physical, one non-physical. Associated with Descartes.

Also known as: cartesian dualism

The principle that everything must have a reason or explanation for why it exists or is the way it is. Nothing "just happens" for no reason.

Also known as: principle of sufficient reason, PSR

Going above and beyond what morality requires. Jumping on a grenade to save others is heroic and praiseworthy, but you can't be blamed for not doing it.

Also known as: supererogatory

When one set of properties depends on another without being identical to it. Mental states supervene on brain states: you can't change the mind without changing the brain.

Also known as: supervenient

When one set of properties depends on another without being reducible to it. Mental states supervene on brain states -- change the brain, change the mind.

Also known as: supervene, supervenient

An argument that agrees with and provides reasons for a statement being true.

Also known as: supporting, supports

A formal argument with premises leading to a conclusion. Example: "All humans are mortal" + "Socrates is human" = "Socrates is mortal."

Also known as: syllogisms

A statement that is true by definition and says nothing meaningful. "It will either rain or it won't." Logically true but uninformative.

Also known as: tautological

An argument for God's existence based on apparent design in nature. "The universe looks designed, therefore there must be a designer."

Also known as: teleological, argument from design

The study of purpose and design. Asks "what is something for?" A teleological explanation of the heart: "it exists to pump blood."

Also known as: teleological, telos

In epistemology, knowledge gained from other people telling you things. Most of what you know came from testimony -- books, teachers, news, conversation.

The belief that God exists and is actively involved in the world. Contrasts with deism (God exists but doesn't intervene).

Also known as: theist, theistic

An attempt to explain why God allows evil and suffering to exist. The classic question: "If God is all-powerful and all-good, why is there evil?"

Also known as: theodicies

The worry that if God knows the future, then the future is fixed and we can't change it. If God already knows what you'll choose, can you really choose differently?

A statement that has been proven to be true using logic, starting from axioms. Unlike theories in science, mathematical theorems are certain once proven.

Also known as: theorems

The idea that what you observe is shaped by the theories you already believe. Two scientists might literally "see" different things when looking at the same data.

Italian philosopher-theologian (1225-1274) who combined Aristotle with Christian theology. Argued for God's existence through five rational proofs. Central figure in Catholic philosophy.

Also known as: Aquinas, Thomist, Thomistic

English philosopher (1588-1679) who argued life without government would be "solitary, poor, nasty, brutish, and short." People need a strong authority to maintain order.

Also known as: Hobbes, Hobbesian

An imaginary scenario used to explore ideas that can't be tested in practice. Famous examples: Schrödinger's cat, the trolley problem, the Chinese room.

Also known as: thought experiments, gedankenexperiment

The view that each particular mental event is identical to some particular brain event, even if the same type of mental state could be realized differently in different brains.

A category or subject area that groups related statements together. Examples: Ethics, Free Will, Consciousness.

Also known as: topics

Being beyond or above the physical world. God's transcendence means existing beyond space, time, and human comprehension.

Also known as: transcendent

The Christian doctrine that God exists as three persons (Father, Son, Holy Spirit) in one being. Three-in-one, not three separate gods.

Also known as: trinitarian

A famous thought experiment: a trolley is heading toward five people. You can divert it to a track with one person. Should you? Tests our moral intuitions about killing vs. letting die.

A theoretical computer that reads and writes symbols on a tape following rules. It's not a real machine -- it's a thought experiment that defines what "computation" means. Any problem a computer can solve, a Turing machine can solve.

Also known as: turing machines

Alan Turing's test for machine intelligence: if a computer can fool a human into thinking it's human through conversation, does it "think"? Debates whether this truly measures intelligence.

The stronger view that each type of mental state (like pain) is identical to a specific type of brain state (like C-fibers firing). The same kind of experience is always the same kind of brain activity.

The problem that the available evidence is always compatible with multiple theories. You can't prove which theory is right just by looking at the data.

Also known as: underdetermined

The belief that all people will eventually be saved or reconciled with God, regardless of their beliefs during life.

Also known as: universalist

An ethical theory that the best action is the one producing the greatest good for the greatest number of people.

Also known as: utilitarian

An argument is valid when the conclusion follows logically from the premises. Even if the premises are false, the structure is correct.

Also known as: valid, logically valid

John Rawls' thought experiment: design society as if you don't know what position you'll occupy. Rich or poor? Healthy or disabled? Smart or average? This removes bias from justice decisions.

Whether a perception accurately represents reality. A veridical perception shows things as they really are. A hallucination is non-veridical.

Also known as: veridical

An ethical approach focused on developing good character traits (virtues) rather than following rules or calculating outcomes.

A thought experiment: imagine a being physically identical to you but with no inner experience. If such a being is conceivable, consciousness might not be reducible to physical processes.

Also known as: p-zombies, philosophical zombie