[idiotsecant]

Which is fine, as long as your assumptions are good models of reality. When your assumptions are essentially articles of faith your models tend to be about as good as the guys who interpret patterns in chicken bones.

[aorist]

You need assumptions exactly for the things which cannot be tested against reality. Otherwise why assume rather than measure?

[JumpCrisscross]

> Otherwise why assume rather than measure?

You need a model to design an experiment.

This is how all science is done. You hypothesize. Then experiment.