Rather it is a secondary need involving the dependence of...

Rather it is a secondary need involving the dependence of the principles of these sciences upon themselves; that is, it is the need for reconfirmation in science, for acquiring further confirmation for these judgments, as in the case of the self-evident propositions concerning which it is said that they depend on the impossibility of a contradiction.

It is clear that the dependence of self-evident propositions on this principle is not of the same kind as the dependence of speculative propositions on self-evident propositions, otherwise the difference between self-evident and speculative propositions would not remain, and at least one proposition, the principle of non-contradiction, has to be accepted as being self-evident.

The Possibility of Knowledge Every rational person is of the belief that he does know things, and that he can know things. Hence he makes an effort to acquire information concerning matters of his needs or interests, and the best sign of this sort of effort is what scientists and philosophers have done by bringing about the various fields of the sciences and philosophy.

Hence the possibility and actuality of science is not something that any rational person whose mind has not been confounded by doubt would deny or even have reservations about. That which is open to discussion or examination and which it is reasonable to disagree about is identification of the frontiers of human knowledge and specification of the means of acquiring certain knowledge, and the way to distinguish correct from incorrect thought, and matters of this kind.

As has been indicated in previous discussions, in Europe, dangerous waves of skepticism have repeatedly appeared, and even great thinkers have been swallowed by it. The history of philosophy remembers schools of thought which absolutely have denied knowledge, such as sophism, skepticism, and agnosticism.

The best explanation of the absolute denial of knowledge (if this charge is correct) is that its victims were afflicted by a severe form of over scrupulousness, a state which affects some people with regard to various other matters as well. Actually it should be considered a kind of mental illness.