Neurath's boat (or Neurath's ship) is a simile used in anti-foundational accounts of knowledge, especially in the philosophy of science. It was first formulated by Otto Neurath. It is based in part on the Ship of Theseus which, however, is standardly used to illustrate other philosophical questions, to do with problems of identity. It was popularised by Willard Van Orman Quine in Word and Object (1960).
Neurath used the simile in several occasions, first in "Problems in War Economics" (1913). In "Anti-Spengler" (1921), he wrote: