Parmenides and Pythagoras, taking views of the Kosmos metaphysical and geometrical rather than physical, supplied the basis upon which Plato's speculations were built. Aristotle recognises Empedokles and Anaxagoras as having approached to his own doctrine--force abstracted or considered apart from substance, yet not absolutely detached from it. This is true about Empedokles to a certain extent, since his theory admits Love and Enmity as agents, the four elements as patients: but it is hardly true about Anaxagoras, in whose theory Noûs imparts nothing more than a momentary shock, exercising what modern chemists call a catalytic agency in originating movement among a stationary and stagnant mass of Homoeomeries, which, as soon as they are liberated from imprisonment, follow inherent tendencies of their own, not receiving any farther impulse or direction from Noûs. [Side-note: Advantage derived from this variety of constructive imagination among the Greeks.] In the number of cosmical theories proposed, from Thales to Demokritus, as well as in the diversity and even discordance of the principles on which they were founded--we note not merely the growth and development of scientific curiosity, but also the spontaneity and exuberance of constructive imagination.[5] This last is a prominent attribute of the Hellenic mind, displayed to the greatest advantage in their poetical, oratorical, historical, artistic, productions, and transferred from thence to minister to their scientific curiosity. None of their known contemporaries showed the like aptitudes, not even the Babylonians and Egyptians, who were diligent in the observation of the heavens. Now the constructive imagination is not less indispensable to the formation of scientific theories than to the compositions of art, although in the two departments it is subject to different conditions, and appeals to different canons and tests in the human mind. Each of these early Hellenic theories, though all were hypotheses and "anticipations of nature," yet as connecting together various facts upon intelligible principles, was a step in advance; while the very number and discordance of them (urged by Sokrates[6] as an argument for discrediting the purpose common to all), was on the whole advantageous. It lessened the mischief arising from the imperfections of each, increased the chance of exposing such imperfections, and prevented the consecration of any one among them (with that inveterate and peremptory orthodoxy which Plato so much admires[7] in the Egyptians) as an infallible dogma and an exclusive mode of looking at facts. All the theorists laboured under the common defect of a scanty and inaccurate experience: all of them were prompted by a vague but powerful emotion of curiosity to connect together the past and present of Nature by some threads intelligible and satisfactory to their own minds; each of them followed out some analogy of his own, such as seemed to carry with it a self-justifying