There is an unbridgeable logical gap between a premise summarizing past observations and a conclusion about the as-yet unobserved.

In the Enquiry, section 4, part 2, Hume presents his famous skeptical argument concerning causation and induction. Since we need “experience” (i.e., the observation of constant conjunctions) to make any causal claims, Hume now asks (EHU 4.14; SBN 32): “What is the foundation of all conclusions from experience?” The conclusion from an experience of constant conjunction is an inference to what has not yet been observed from what has already been observed, and Hume finds an unbridgeable gap between