Abstract

It is often claimed that the conclusion of a deductively valid argument is contained in its premises. Popper refuted this claim when he showed that an empirical theory can be expected always to have logical consequences that transcend the current understanding of the theory. This implies that no formalisation of an empirical theory will enable the derivation of all its logical consequences. I call this result ‘Popper-incompleteness.’ This result appears to be consistent with the view of deductive reasoning as a process of unfurling the content of the premises; but I suggest that the result about validity impugns this theory of reasoning.