The movement is not at one step: it has a middle term or mean which often seems as if it were a step backward. Progress in knowledge is usually described as produced by the mode of demonstration or the mode of experience. Formal Logic prefers the first mode of describing it: Applied Logic prefers the second. Either mode may serve, if we properly comprehend what demonstration and experience mean. And that will not be done unless we keep equally before us the affirmative and the negative element in the process. The law of rational progress in knowledge, of the dialectical movement of consciousness, or in one word of experience, is not simple movement in a straight line, but movement by negation and absorption of the premisses. The conclusion or the new object of knowledge is a product into which the preceding object is reduced or absorbed. Thus the movement from faith (which is concentrated and wholly personal knowledge) to open and universal knowledge, which is capable of becoming the possession of a community,--truth and not merely conviction, must pass through doubt. The premisses from which we start, and the original object with which we begin, are not left _in statu quo_: they are destroyed in their own shape, and become only materials to build up a new object and a conclusion. It is on the stepping-stones of discarded ideas that we rise to higher truth: and it is on the abrogation of the old objects of knowledge that the new objects are founded. Not merely does a new object come in to supplement the old, and correct its inadequacies by the new presence: not merely do _we_ add new ranges to _our_ powers of vision, retaining the old faculties and subjoining others. The whole world--alike inward and outward,--the consciousness and its object--is subjected to a thorough renovation: every feature is modified, and the system re-created. The old perishes: but in perishing contributes to constitute the new. Thus the new is at once the affirmation and negation of the old. And such is the invariable nature of intelligent progress, of which the old and not a few modern logicians failed to render a right account, because they missed the negative element, and did not see that the immediate premisses must be abolished in order to secure a conclusion,--even as the grapes must be crushed before the wine can be obtained.