Some sciences, like chemistry and biology, or biology and anthropology, are parted only, we presume, by accidental gaps in human knowledge; a more minute and better directed study of these fields would doubtless disclose their continuity with the fields adjoining. But there is one general division in science which cuts almost to the roots of human experience. Human understanding has used from the beginning a double method of surveying and arresting ideally the irreparable flux of being. One expedient has been to notice and identify similarities of character, recurrent types, in the phenomena that pass before it or in its own operations; the other expedient has been to note and combine in one complex object characters which occur and reappear together. The latter feat which is made easy by the fact that when various senses are stimulated at once the inward instinctive reaction—which is felt by a primitive mind more powerfully than any external image—is one and not consciously divisible.
The first expedient imposes on the flux what we call ideas, which are concretions in discourse, terms employed in thought and language. The second expedient separates the same flux into what we call things, which are concretions in existence, complexes of qualities subsisting in space and time, having definable dynamic relations there and a traceable history. Carrying out this primitive diversity in reflection science has moved in two different directions. By refining concretions in discourse it has attained to mathematics, logic, and the dialectical developments of ethics; by tracing concretions in existence it has reached the various natural and historical sciences. Following ancient usage, I shall take the liberty of calling the whole group of sciences which elaborates ideas dialectic, and the whole group that describes existences physics.
The contrast between ideal science or dialectic and natural science or physics is as great as the understanding of a single experience could well afford; yet the two kinds of science are far from independent. They touch at their basis and they co-operate in their results. Were dialectic made clearer or physics deeper than it commonly is, these points of contact would doubtless be multiplied; but even as they stand they furnish a sufficient illustration of the principle that all science develops objects in their own category and gives the mind dominion over the flux of matter by discovering its form.
Their mutual implication.
That physics and dialectic touch at their basis may be shown by a double analysis. In the first place, it is clear that the science of existence, like all science, is itself discourse, and that before concretions in existence can be discovered, and groups of coexistent qualities can be recognised, these qualities themselves must be arrested by the mind, noted, and identified in their recurrences. But these terms, bandied about in scientific discourse, are so many essences and pure ideas: so that the inmost texture of natural science is logical, and the whole force of any observation made upon the outer world lies in the constancy and mutual relations of the terms it is made in. If down did not mean down and motion motion, Newton could never have taken note of the fall of his apple. Now the constancy and relation of meanings is something meant, it is something created by insight and intent and is altogether dialectical; so that the science of existence is a portion of the art of discourse.
On the other hand discourse, in its operation, is a part of existence. That truth or logical cogency is not itself an existence can be proved dialectically,[A] and is obvious to any one who sees for a moment what truth means, especially if he remembers at the same time that all existence is mutable, which it is the essence of truth not to be. But the knowledge or discovery of truth is an event in time, an incident in the flux of existence, and therefore a matter for natural science to study.
Furthermore, every term which dialectic uses is originally given embodied; in other words, it is given as an element in the actual flux, it conies by illustration. Though meaning is the object of an ideal function, and signification is inwardly appreciable only in terms of signification, yet the ideal leap is made from a material datum: that in which signification is seen is a fact. Or to state the matter somewhat differently, truth is not self-generating; if it were it would be a falsehood.
Its eternity, and the infinitude of propositions it contains, remain potential and unapproachable until their incidence is found in existence. Form cannot of itself decide which of all possible forms shall be real; in their ideality, and without reference to their illustration in things, all consistent propositions would be equally valid and equally trivial. Important truth is truth about something, not truth about truth; and although a single datum might suffice to give foothold and pertinence to an infinity of truths, as one atom would posit all geometry, geometry, if there were no space, would be, if I may say so, all of the fourth dimension, and arithmetic, if there were no pulses or chasms in being, would be all algebra. Truth depends upon facts for its perspective, since facts select truths and decide which truths shall be mere possibilities and which shall be the eternal forms of actual things. The dialectical world would be a trackless desert if the existent world had no arbitrary constitution. Living dialectic comes to clarify existence; it turns into meanings the actual forms of things by reflecting upon them, and by making them intended subjects of discourse.
Their co-operation.
Dialectic and physics, thus united at their basis, meet again in their results. In mechanical science, which is the best part of physics, mathematics, which is the best part of dialectic, plays a predominant rôle; it furnishes the whole method of understanding wherever there is any real understanding at all. In psychology and history, too, although dialectic is soon choked by the cross-currents of nature, it furnishes the little perspicuousness which there is. We understand actions and mental developments when the purposes or ideas contained in any stage are carried out logically in the sequel; it is when conduct and growth are rational, that is, when they are dialectical, that we think we have found the true secret and significance of them. It is the evident ideal of physics, in every department, to attain such an insight into causes that the effects actually given may be thence deduced; and deduction is another name for dialectic. To be sure, the dialectic applicable to material processes and to human life is one in which the terms and the categories needed are still exceedingly numerous and vague: a little logic is all that can be read into the cataract of events. But the hope of science, a hope which is supported by every success it scores, is that a simpler law than has yet been discovered will be found to connect units subtler than those yet known; and that in these finer terms the universal mechanism may be exhaustively rendered. Mechanism is the ideal of physics, because it is the infusion of a maximum of mathematical necessity into the flux of real things. It is the aspiration of natural science to be as dialectical as possible, and thus, in their ideal, both branches of science are brought together.