758 EVOLUTION writings of the Middle Ages, including those of the school men, we find no progress towards a more accurate and scientific view of nature. The cosmology of this period consists for the most part of the Aristotelian teleological view of nature combined with the Christian idea of the Deity and His relation to the world. In certain writers, however, there appears a more elaborate transformation of the doc trine of creation into a system of emanation. According to John Scotus Erigena, the nothing out of which the world is created is the divine essence. Creation is the act by which God passes through the primordial causes, or univer sal ideas, into the region of particular things (processio), in order finally to return to himself (reversio). The transition from the universal to the particular is of course conceived as a descent or degradation. A similar doctrine of emana tion is to be found in the writings of Bernhard of Chartres, who conceives the process of the unfolding of the world as a movement in a circle from the most general to the indivi dual, and from this back to the most general. This move ment is said to go forth from God to the animated heaven, stars, visible world, and man, which represent decreasing degrees of cognition. Arab Philosophers. Elaborate doctrines of emanation, largely based on Neo-Platonic ideas, are also propounded by some of the Arabic philosophers, as by Alfarabi and Avicenna. The leading thought is that of a descending series of intelligences, each emanating from its predecessor, and having its appropriate region in the universe. Jewish Philosophy. In the Jewish speculations of the Middle Ages may be found curious forms of the doctrine of emanations, uniting the Biblical idea of creation with elements drawn from the Persians and the Greeks. In the later and developed form of the Cabala, the origin of the world is represented as a gradually descending emanation of the lower out of the higher. Among the philosophic Jaws, the Spanish Avicebron, in his Fons Vitce, expounds a curious doctrine of emanation. Here the divine will is viewed as an efflux from the divine wisdom, as the inter mediate link between God, the first substance and all things, and as the fountain out of which all forms emanate. At the same time all forms, including the higher intelligible ones, are said to have their existence only in matter. Matter is the one universal substance, body and mind being merely specifications of this. Thus Avicebron approaches, as M. Munk observes, 1 a pantheistic conception of the world, though he distinctly denies both matter and form to God. Later Scholastics. Passing now to the later schoolmen, a bare mention must be made of Thomas, who elaborately argues for the absolute creation of the world out of nothing, and of Albsrtus Magnus, who reasons against the Aristo telian idea of the past eternity of the world. More import ance attaches to Duns Scotus, who brings prominently for ward the idea of a progressive development in nature by means of a process of determination. The original sub stance of the world is the materia primo-prima, which is the immediate creation of the Deity. This serves Duns Scotus as the most universal basis of existence, all angels having material bodies. This matter is differentiated into particular things (which are not privations but perfections) through the addition of an individualizing principle (hcecceitas) to the universal (quidditas). The whole world 13 represented by the figure of a tree, of which the seeds and roots are the first indeterminate matter, the leaves the accidents, the twigs and branches corruptible creatures, the ossoms the rational soul, and the fruit pure spirits or angels. It is also described as a bifurcation of two twi^s, nental and bodily creation out of a common root. One 1 Melanges de philosophic juive et arabe, p. 225. might almost say that Duns Scotus recognizes the principle of a gradual physical evolution, only that he chooses to re present the mechanism by which the process is brought about by means of quaint scholastic fictions. Revival of Learning. The period of the revival of learn ing, which was also that of a renewed study of nature, is marked by a considerable amount of speculation respecting the origin of the universe. In some of these we see a re turn to Greek theories, though the influence of physical dis coveries, more especially those of Copernicus, Kepler, and Galileo, is distinctly traceable. Telesio. An example of a return to early Greek specu lation is to be met with in Bernardino Telesio. By this writer the world is explained as a product of three prin ciples, dead matter, and two active forces, heat and cold. Terrestrial things arise through a confluence of heat, which issues from the heavens, and cold, which comes from the earth. Both principles have sensibility, and thus all pro ducts of their collision are sentient, that is, feel pleasure and pain. The superiority of animals to plants and metals in the possession of special organs of sense is connected with the greater complexity and heterogeneity of their structure. Giordano Bruno. In the system of Giordano Bruno, who sought to construct a philosophy of nature on the basis of new scientific ideas, more particularly the doctrine of Copernicus, we find the outlines of a theory of cosmic evolution conceived as an essentially vital process. Matter and form are here identified, and the evolution of the world is presented as the unfolding of the world-spirit to its perfect forms according to the plastic substratum (matter) which is but one of its sides. This process of change is con ceived as a transformation, in appearance only, of the real unchanging substance (matter and form). All parts of matter are capable of developing into all forms; thus the materials of the table and chair may, under proper cir cumstances, be developed to the life of the plant or of the animal. The elementary parts of existence are the minima, or monads, which are at once material and mental, On their material side they are not absolutely unextended, but spherical. Bruno looked on our solar system as but one out of an infinite number of worlds. His theory of evolution is essentially pantheistic, and he does not employ his hypothesis of monads in order to work out a more mechanical conception. Campanella. A word must be given to one of Bruno s contemporary compatriots, namely Campanella, who gave poetic expression to that system of universal vitalism which Bruno developed. He argues, from the principle quic- quid est in ejfectibus esse et in causis, that the elements and the whole world have sensation, and thus be appears to derive the organic part of nature out of the so-called " inor ganic." B^ehme. Anotherwriter of this transition period deserves a passing reference here, namely, Jacob Boehme the mystic, who by his conception of a process of inner diremption as the essential character of all mind, and so of God, prepared the way for later German theories of the origin of the world as the self-differentiation and self-externalization of the absolute spirit. Holies and Gassench. The influence of an advancing study of nature, which was stimulated if not guided by Bacon s writings, is seen in the more careful doctrines of materialism worked out almost simultaneously by Hobbes and Gassendi. These theories, however, contain little that bears directly on the hypothesis of a natural evolution of things. In the view of Hobbes, the difficulty of the genesis of conscious minds is solved by saying that sensa tion and thought are part of the reaction of the organism on external movement. Yet Hobbes appears (as Clarke
points out) to have vaguely felt the difficulty; and in a