1. We have as many psychological laws of development as we had laws of relation, and the former may be regarded as the application of the latter to more comprehensive psychical [p. 326] interconnections. We designate the laws in question as those of mental growth of heterogony of ends, and of development, towards opposites.
2. The law of mental growth is as little applicable to all contents of psychical experience as any other psychological law of development.
It holds only under the limiting condition under which the law of resultants, whose application it -is, holds, namely under the condition of the continuity of the processes (p. 323). But since the circumstances that tend to prevent the realization of this condition, are, of course, much more frequent when the mental developments concerned include a greater number of psychical syntheses, than they axe in the single syntheses themselves, it follows that the law of mental growth can be demonstrated only for certain developments taking place under normal conditions, and even here only within certain limits. Within these limits, however, the more comprehensive developments, as, for example, the mental development of the normal individual and the development of mental communities, are obviously the best exemplifications of the fundamental law of resultants which lies at the basis of this development.
3. The law of heterogony of ends is most closely connected with the law of relations, but it is also based on the law of resultants, which is always to be taken into consideration when dealing with the larger interconnections of psychical development. In fact, we may regard this law as a principle of development which controls the changes arising, as results of successive creative syntheses, in the relations between the single partial contents of psychical compounds. The resultants arising from united psychical processes include contents that were not present in the components, and these new contents may in turn enter into relation with the old components thus changing again the relations between these old components [p. 327] and consequently the new resultants that arise from them. This principle of continually changing relations is most striking when an idea of ends is formed on the basis of the given relations. Here the relation of the single factors to one another is regarded as an interconnection Of means which has for the end aimed at, the product arising from the interconnection. The relation between the actual effects in such a case and the ideated ends is such that secondary effects always arise that were not thought of in the first ideas of end. These new effects enter into new series of motives, and thus modify the old ends or add new ones to them.
The principle of heterogony of ends in its broadest sense dominates all psychical processes. In the special teleological coloring which has given it its name, however, it is to be found primarily in the sphere of volitional processes, for here the ideas of end attended by their affective, motives are of the chief importance. In the various spheres of applied psychology it is therefore especially ethics for which this law is of great importance.
4. The law of development towards opposites is an application of the law of intensification through contrast, to more comprehensive interconnections which form in themselves series of developments. These series, in accordance with the fundamental law of contrasts, are of such a character that feelings and impulses which were of small intensity at first, increase gradually in intensity through contrast with feelings of opposite quality that were for a time predominant, until, finally, they gain the ascendency over the formerly predominant feelings and are themselves for a longer or shorter time in control. From this point the same alternation may be once or even several times repeated. But generally the principles of mental growth and heterogony of ends operate in the case of such an oscillation, so that succeeding phases are like [p. 328] corresponding antecedent phases in their general affective direction, but still essentially different in their special components.
The law of development towards opposites shows itself in the mental development of the individual, partly in a purely individual way within shorter periods of time, and partly in certain universal regularities in the relation of various periods of life. It has long been recognized that the predominating temperaments of different periods of life present certain contrasts. Thus, the light, sanguine excitability of childhood, which is seldom more than superficial, is followed by the slower but more retentive temperament of youth with its frequent touch of melancholy. Then comes manhood with its mature character, generally quick and active in decision and execution, and last of all, old age with its leaning toward contemplative quiet. Even more than in the individual does this principle of antithesis find expression in the alternation of mental tendencies that appear in the social and historical life of communities, and in the reactions of these tendencies on civilization and customs and on social and political development. In the same way that the principle of heterogony of ends applied chiefly to the domain of moral life, this principle of development towards opposites finds its chief significance in the more general sphere of historical life .