American Dictionary of the English Language

SUPPOSI'TION, noun The act of laying down, imagining or admitting as true or existing, what is known not to be true, or what is not proved.

1. The position of something known not to be true or not proved; hypothesis.

This is only an infallibility upon supposition that if a thing be true, it is impossible to be false.

2. Imagination; belief without full evidence.