Some learned men have maintained that we can know nothing. The truth is better stated by St. Paul: “If a man thinks that he knows anything, he knows nothing as he ought,” that is nothing other than imperfectly. It is the more difficult to deal systematically with this matter, because we want, in our tongue, words of such relative meaning as _scire_, _cognoscere_, _intelligere_, etc. I propose only to run together a few such observations as simple good sense can make, and accept, and find use for. A great and increasing proportion of persons would, if you asked them, maintain that all convictions are merely opinions. But it is not so. A fool may opine absolutely that a wise man is a fool, but the wise man knows that the fool is one. The same or opposite conclusions, political or otherwise, may be arrived at by two persons from a view of the same facts, and each may be equally confident; but the conclusions of one may be knowledge, and those of the other opinion. The reality of the difference is indicated by the difference of the feelings which commonly subsist between those who opine and those who know. Those who opine hate those who know, and who speak as those who know. They think it an assumption of superiority, whereas it is only its reality, and cannot but appear more or less in its manner of expression. Those who know, are only contemptuous or indifferent towards such as impudently or ignorantly opine. The consequence is that the knowledge which is wisdom is nowhere, as an acknowledged force and factor in worldly affairs, and is only able to assert itself _sub rosa_, or by accident, or by the more or less underhand management of folly and ignorance. What most people call “deep and earnest convictions” on political and social topics are generally muddle-headed medleys of knowledge of fact and opinion. They know that such and such a thing is an evil, and they opine that they see a way to amend it; and if wiser people point out to them that the evil would not be so amended, or that greater evils would accrue from the attempt, they only feel that their “convictions” are affronted and opposed by cold-blooded calculations. This kind of opinion is often as confident as actual knowledge. When Carlyle said that it was impossible to believe a lie, he can only have meant that it was impossible to believe it with that highest kind of certitude which consists in intellectual perception. Probably no one could believe a lie with that degree of faith which would enable him to suffer deliberate martyrdom for it. Protestant and Catholic martyrs have usually been sufferers for one and the same faith, or, at least, parts of the same faith, in which parts they have considered the whole to be involved. Very few, if any, have ever carried the courage of mere “opinions” to the stake.