The Philosophy of 'As if'

The Philosophy of 'As if': A System of the Theoretical, Practical and Religious Fictions of Mankind (German: Die Philosophie des Als Ob) is a 1911 book by the German philosopher Hans Vaihinger, based on his dissertation of 1877. The work for which Vaihinger is best known, it was published in an English translation by C. K. Ogden in 1924. In 1935, a revised and abbreviated English translation by Ogden was published. The revised translation was based on the sixth German edition of the original work. Routledge published a new edition of the book in 2021 with a new foreword by Michael A. Rosenthal in its 'Routledge Classics' imprint.

Within a philosophical framework of epistemology, the book argues for false premises or false assumptions as a viable cognitive heuristic. For example, simplified models used in the physical sciences are often formally false, but nevertheless close enough to the truth to furnish useful insight; this is understood as a form of idealization.