assert

v.

1. To state positively

   state, say, declare, affirm, aver, avow, avouch, attest, profess, asseverate, warrant*; see also declare 1.

2. To maintain

   cite, allege, advance; see support 2.

to assert is to state positively with great confidence but with no objective proof to assert that human nature will never change; to declare is to assert openly or formally, often in the face of opposition they declared their independence; affirm implies deep conviction in one's statement or the unlikelihood of denial by another she affirmed her innocence; aver connotes implicit confidence in the truth of one's statement from one's own knowledge of the matter; avouch implies firsthand knowledge or authority on the part of the speaker; warrant, in this comparison, is colloquial, and implies positiveness by the speaker I warrant they'll be late again See also syn. study at declare.