posit

Concise Oxford English Dictionary © 2008 Oxford University Press:
posit /ˈpɒzɪt/

▶verb (posits, positing, posited)

• 1 put forward as fact or as a basis for argument.

  ■ (posit something on) base something on the truth of (a particular assumption).

• 2 place.

▶noun Philosophy a statement which is made on the assumption that it will prove to be true.

– origin C17: from L. posit-, ponere ‘place’.