Should we look for knowledge or certainty

Deduction (stepping on previous truths and making an inference) is the only way to be certain of a proposition. But certainty is not the same as knowledge.Induction, on the other hand, is the proposal of a general principle, based on the regularity of a some observations.Deduction (the use of logic) makes me very certain, but adds very little knowledge to me: the deducted truth is already into the previous ones (the premises).Induction let me jump on completely new truths. But, who can guarantee that “swans are white” just because all that I have seen, happen to be white? Induction gives me joy of novelty, but, seldom, the comfort of certainty.The moral of this story is: knowledge, as any human growth operation (like love, or virtue) can on be achieved “dialectically”, zigzaging between opposites. Forget about finding an optimun.