It is only those who are ignorant and uncultivated who can know anything at all in a proper sense of the words.  Cultivation will breed in any man a certainty of the uncertainty even of his most assured convictions.  It is perhaps fortunate for our comfort that we can none of us be cultivated upon very many subjects, so that considerable scope for assurance will still remain to us; but however this may be, we certainly observe it as a fact that the greatest men are they who are most uncertain in spite of certainty, and at the same time most certain in spite of uncertainty, and who are thus best able to feel that there is nothing in such complete harmony with itself as a flat contradiction in terms. — Samuel Butler