from those of visible bodies. The whole physical universe may be represented in the imagination as an aggregate of bodies participating in motions of extraordinary complexity, but of one type. But now let the emphasis be placed upon the determining causes rather than upon the moving bodies themselves. In other words, let the bodies be regarded as attributive and the forces as substantive. The result is a radical alteration of the mechanical scheme and the transcendence of common-sense imagery. This was one direction of outgrowth from the work of Newton. His force of gravitation prevailed between bodies separated by spaces of great magnitude. Certain of the followers of Newton, notably Cotes, accepting the formulas of the master but neglecting his allusions to the agency of God, accepted the principle of action at a distance. Force, in short, was conceived to pervade space of itself. But if force be granted this substantial and self-dependent character, what further need is there of matter as a separate form of entity? For does not the presence of matter consist essentially in resistance, itself a case of force? Such reflections as these led Boscovich and others to the radical departure of defining material particles as centres of force.

§ 108. But a more fruitful hypothesis of t same general order is due to the attention directe The Develop to the conception of energy, or capaci

ment and Ex

Conception

of Energy.

tension of the for work, by experimental discoverie of the possibility of reciprocal tran formations without loss, of motion, heat, electris ity, and other processes. The principle of the conservation of energy affirms the quantitative constancy of that which is so transformed, meas ured, for example, in terms of capacity to move units of mass against gravity. The exponents of what is called "energetics" have in many cases come to regard that the quantity of which is so conserved, as a substantial reality whose forms and distributions compose nature. A contemporary scientist, whose synthetic and dogmatic habit of mind has made him eminent in the ranks of popu lar philosophy, writes as follows:

"Mechanical and chemical energy, sound and heat, light and electricity, are mutually convertible; they seem to be but different modes of one and the same fundamental force or energy. Thence follows the important thesis of the unity of all natural forces, or, as it may also be expressed, the 'monism of energy.'

Haeckel: Riddle of the Universe.

Cabe, p. 254.

Translation by Mc

The best systematic presentation of energetics" is to be found in Ostwald's Vorlesungen über Natur-Philosophie.

V.

The conception of energy seems, indeed, to afford an exceptional opportunity to naturalism. We have seen that the matter-motion theory was satisfied to ignore, or regard as insoluble, problems concerning the ultimate causes of things. Furthermore, as we shall presently see to better advantage, the more strictly materialistic type of naturalism must regard thought as an anomaly, and has no little difficulty with life. But the conception of energy is more adaptable, and hence better qualified to serve as a common denominator for various aspects of experience. The very readiness with which we can picture the corpuscular scheme is a source of embarrassment to the seeker after unity. That which is so distinct is bristling with incompatibilities. The most aggressive materialist hesitates to describe thought as a motion of bodies in space. Energy, on the other hand, exacts little if anything beyond the character of measurable power. Thought is at any rate in some sense a power, and to some degree measurable. Recent discoveries of the dependence of capacity for mental exertion upon physical vitality and measurements of chemical energy received into the system

Herbert Spencer, in his well-known First Principles, makes philosophical use of both "force" and "energy."

“

as food, and somehow exhausted by the activitie of thought, have lent plausibility to the hypothesi of a universal energy of which physical and " PST chical" processes are alike manifestations. And the conception of energy seems capable not only of unifying nature, but also of satisfying the metaphysical demand for an efficient and moving cause. This term, like "force" and " power," is endowed with such a significance by common sense. Indeed, naturalism would seem here to have swung round toward its hylozoistic startingpoint. The exponent of energetics, like the naive animistic thinker, attributes to nature a power like that which he feels welling up within himself. When he acts upon the environment, like meets like. Energetics, it is true, may obtain a definite meaning for its central conception from the measurable behavior of external bodies, and a meaning that may be quite free from vitalism or teleology. But in his extension of the conception the author of a philosophical energetics abandons this strict meaning, and blends his thought even with a phase of subjectivism, known as panpsychism. This theory regards the inward life of all nature as homogeneous with an immediately felt activity. or

Cf. Chap. IX.

appetency, as energetics finds the inner life to be homogeneous with the forces of nature. Both owe their philosophical appeal to their apparent success in unifying the world upon a direct empirical basis, and to their provision for the practical sense of reality.

Such, in brief, are the main alternatives available for a naturalistic theory of being, in consequence of the historical development of the fundamental conceptions of natural science.

§ 109. We turn now to an examination of the manner in which naturalism, equipped with workThe Claims of ing principles, seeks to meet the special Naturalism. requirements of philosophy. The conception of the unity of nature is directly in the line of a purely scientific development, but naturalism takes the bold and radical step of regarding nature so unified as coextensive with the real, or at any rate knowable, universe. It will be remembered that among the early Greeks Anaxagoras had referred the creative and formative processes of nature to a non-natural or rational agency, which he called the Nous. The adventitious character of this principle, the external and almost purely nominal part which it played in the actual cosmology of Anaxagoras, betrayed it into the hands