Russell's substitutional theory shows that eliminating classes via propositional functions requires intensional distinctions that extensionality actively destroys, making derivation circular.
?Rate how convincing each reason is below to see the overall strength.
No one has weighed in yet. Be the first to share reasons for or against this statement.
Sign in or register to share your perspective on this statement.
Russell's attempt to solve a logical problem by replacing references to abstract objects (like classes or sets) with descriptions of concrete things instead.
extensional(logic and philosophy of probability)
A property of relations (like material implication) that Nagel claimed Reichenbach's probability implication lacks
extensionality(classical logic and regimentation of theories)
The property of a theory whereby a predicate may be replaced by a co-extensive predicate without change of truth-value of the containing sentence, and likewise an embedded sentence may be replaced by a sentence of the same truth-value
intensional(as used in logic and philosophy of language)
Relating to meaning, context, or how something is described, rather than just what the thing is—for example, 'the morning star' and 'the evening star' refer to the same object (Venus) but intensionally they're different descriptions.
propositional functions(PM's logical system)
A foundational element of the logic of Principia Mathematica (PM), distinct from Frege's use of concepts (functions from objects to truth values)