And with regard to the diffusion of knowledge, this, though it brings more grist to the intellectual mill, can have no effect in raising the mean standard of excellence in the mill itself. There is more to grind; but this does not improve the grinding apparatus; or, if it does, it tells so far against Professor Weismann's hypothesis. To vary the analogy, the diffusion of knowledge increases the store of available food; but it does not bring with it any additional power of digesting the food; or, if it does, it may be through inherited increments of mean digestive power.
It may, however, be maintained that there is no conclusive proof that the mean intellectual level of Englishmen to-day is any higher than it was in the days of the Tudors. If so, of course, my argument falls to the ground. I have no desire to dogmatize on the subject. I merely set down the reasons, such as they are, and for what they are worth, which lead me to entertain a general belief that the intellectual progress of Englishmen during the past three hundred years has been in part due to the inheritance of individually acquired faculty.
Mental evolution, then, is the metakinetic equivalent of interneural, or, in us vertebrates, brain-evolution. The brain forms a kinetic system in some sense independent of, and yet in constant touch with, the kinetic system of the world around. Its kineses, though they do not resemble, yet more or less accurately represent or symbolize, the kineses of the surrounding universe. As the kineses of the world around are interdependent and harmonious, so are the neural kineses of the brain interdependent and harmonious. And no modification of this kinesis which is out of harmony with the kinetic system already established in the brain can be incorporated with that existing system. Such attempted modification is eliminated through incongruity.
Associated with this brain-kinesis, and forming its inner aspect, is a metakinetic system in which the higher manifestations rise to the level of full consciousness; others form sub-conscious states; others are unconscious. But the whole form a coherent system answering to the coherent kinetic system.
Consciousness is thus associated only with the phenomena of that kinetic microcosm which we call the brain (or other interneural system). Obviously, therefore, it does not and cannot deal directly with anything outside the brain. Its knowledge is solely and entirely a knowledge of the representative occurrences of the interneural system. But out of these occurrences a surrounding world of phenomena is constructed in mental symbolism.
The brain itself, however, is part of the world of phenomena thus constructed in mental symbolism; and the world, therefore, dissolves in pure idealism, leaving only a fleeting series of states of consciousness, if we do not assume the existence of a system of "things in themselves" (noumena), of which kineses and metakineses are the phenomenal manifestations. Whether the "things in themselves" in any sense resemble their phenomenal manifestations, we cannot say. It is as difficult philosophically to conceive that they can as it is practically to conceive that they do not. And since, whether they do or do not, the world we live in is phenomenal; since it is to phenomena that we have to adapt our conduct; since it is with phenomena that all our thoughts and emotions have reference; since the world we construct in mental symbolism is the world in which we live and move and have our being; it is not only convenient, but logically justifiable, to call this world of phenomena the really existing world for us human-folk and other sentient organisms.
As in the kinetic interneural system, or brain, so, too, in the metakinetic system, no modification of the metakinesis which is out of harmony with the existing metakinesis can be incorporated therewith. Such attempted modification is eliminated through incongruity.
In the lower stages of mental evolution, those which belong to the perceptual sphere, where the neuroses are closely connected with the life-preserving activities of the organism, the survival or non-survival of the system of neuroses is largely dependent on the fitness of the associated activities to the conditions of life. But in the higher stages of mental evolution, those which belong to the conceptual sphere, the connection of certain brain-neuroses with life-preserving motor-activities becomes less close and direct. The corresponding ideas, thoughts, and emotions become floated off into a more abstract region. Here the system of ideas, as such, that is to say, so far as they are removed from life-preserving activities, is determined mainly by the law of congruity. But there are several such systems. There are, indeed, as many systems as there are minds; but these may be classified in several distinct groups, which we may liken to genera and species. These are the various interpretations of nature, theories of things, and the like; the systems of ideas, thoughts, conceptions, emotions, beliefs, which, as we say, belong to us, each and all, and which determine to which metakinetic species we belong. These are the highest products of mental evolution; and among them there is, so to speak, a struggle, if not for existence, at any rate for prevalence. Which shall eventually prevail—a spiritual interpretation of nature, a material interpretation, a monistic interpretation, or other, who shall say? But, so far as we can judge, the winning species among systems of ideas and interpretations of nature are likely to be those in which the greatest number of ideas are fused into harmonious synthesis; in which all the ideas are congruous; and in which the abstract or conceptual ideas, when brought into contact with concrete or perceptual states of consciousness, are found to be in harmony and congruity therewith.