First published Thu Sep 17, 2009; substantive revision Thu Apr 27, 2023 According to David Hume, the impossible cannot be conceived. Moritz Schlick claimed that the logically impossible, such as an explicit inconsistency, is simply unthinkable. Yet Hegel complained that it is “one of the fundamental prejudices of logic as hitherto understood” that “the contradictory cannot be imagined or thought”