All human conscious reasoning is based on assumptions, and much of it involves presuppositions, of which again a large part tends to be prejudice.

There is nothing necessarily wrong or mistaken about presuppositions, except that one cannot consciously reckon with what one is not conscious of while tacitly using it.

Hence one important task of both philosophy and logic, in practice, is the teasing out of the presuppositions of arguments, both to see whether they entail or support the conclusions they are used for, and to find out whether once explicated they are true or probable or not.