Abstract

A deduction is a type of inference that aims for validity and, consequently, can be valid. But an invalid deduction could never be valid because a single possible world where a deductive inference is valid would “spread,” so to speak, its validity across all remaining possible worlds. If the only genuine deductions are the valid ones, then our talk about deduction is an indirect way of referring to validity rather than an inference type. There is simply no deduction to speak of—only validity. But then again, it’s clear that validity is an attribute that some inferences possess, while others do not. This is a paradox.