We cannot derive it from our senses, for our senses deceive us, says Lamennais. That the senses conjointly correct such false impressions as each sense separately produces, is a fact of which he does not take cognisance. We are, in his opinion, the less certain of any necessary connection between the impressions of our senses and the reality of things, from our not even being certain of our own existence. How we, if we are not certain of that, can be certain of anything whatsoever, is a question he leaves unanswered. Conviction, the inward feeling that the thing must be so, is, he affirms, as deceptive as are the impressions of the senses. The irresistible force with which a principle imposes itself upon our reason affords no proof of the truth of that principle. Error is always possible. That one may quite well acknowledge one's fallibility generally speaking, and yet regard one's self as certain of the truth in many single, definite cases, is another fact he leaves out of reckoning. Next comes the turn of scientific research or reasoning. This, he maintains, leads to doubt of everything, for the highest of all principles do not admit of proof; we are not certain, moreover, of the reliability of memory. It is impossible to parry this attack upon the scientific method in so far that it is of course impossible to prove the reliability of memory without pre-supposing the reliability of the memory which is to be proved. But of the indirect proofs of the reliability of memory provided by human experience Lamennais does not say a single word.