Faith differs from knowledge. There are some things which we know to be true, and there are others of which we say we believe them to be true. There are certain truths which are termed axiomatic. When the terms in which they are expressed are understood, the truth they convey is at once admitted. We know that two and two make four, we know that two straight lines cannot enclose a space; but we do not know in the same sense those things which the Creed affirms. It deals with statements that, for the most part, have never been, and cannot be, tested by sense, and that cannot be demonstrated by such proof as will compel us to accept them. We believe them, not because it is impossible to withhold our assent, nor only because nature, history, and conscience confirm them, but on the ground of testimony. "Faith cometh by hearing, and hearing by the Word of God."[010] We believe because we are assured on sufficient and competent authority that these things are so. We know that we live in a material universe, but our knowledge does not extend to the manner in which the universe came into being. That is a matter of belief. "Through faith"--not by ocular or logical proof, but on testimony--"we understand that the worlds were framed by the Word of God."[011] Faith differs from opinion. When a man believes his mind is made up. By whatever process it may have been reached, the conclusion commends itself as one that is fixed and irreversible. Opinion, on the other hand, is held loosely. It is based not on certainty but on probability. The possibility of error is recognised, and the opinion is readily surrendered when the grounds on which it was formed are seen to be insufficient or misleading. "A man," says Coleridge, "having seen a million moss roses all red, concludes from his own experience and that of others that all moss roses are red. That is a maxim with him--the _greatest_ amount of his knowledge upon the subject. But it is only true until some gardener has produced a white moss rose,--after which the maxim is good for nothing."[012]