PERIPATETICS (ireporarnTocot) is the name given to an ancient philosophical sect. It was so designated from the circumstance of its founder, Aristotle, being accustomed to deliver his doctrines while walking in the grove of the Lyceum in the suburbs of Athens. [Arm. TOTLE, in Moo. Div.] There is scarcely any department of human knowledge of which the writings of Aristotle do not treat. It would far exceed the limits of this article to give a full detail of his opinions. Such of them only as characterised the school which he originated can be referred to, and even these must be briefly noticed. They have relation chiefly to his general physical and metaphysical principles. To his system of logic, with the additions subsequently made to it by his disciples, it is unnecessary particularly to advert. (0aoalloN.) Previous to Aristotle's time it was commonly supposed by those who had speculated respecting the origin of the universe, that there is an eternal substance from which bodies are made, and on which forms are impressed, and to which the name of matter was assigned. This matter was understood to have been always in motion, to consist of indefi nitely small particles, and to have been collected and united in bodies by the agency of an intelligent principle. It was further supposed that the original particles had certain properties by which they differed from each other, and by which the constitution of the bodies which they composed was determined. Empedocles and others taught that there were four primary elements, which are the bases of all corporeal forma; Anaxagoras and his followers maintained that bodies exactly represent the form of each of their constituent particles : while Plato held that essential forms have an actual existence in the divinity, and that by the union of these with matter the formation of bodies is effected.
Rejecting all these theories, Aristotle assumed the underived and independent existence of two opposite principles. But since such prin ciples by their contrariety would destroy each other, the existence of a third was requisite. These he conceived to be matter, form, and privation, the first two being the constituent principles of things, and the last being accidentally connected with them. The first matter was
imagined to be entirely destitute of all qualities, to exist potentially, and to be the subject in which forms are made to inhere. Form he explained to be the essence of a thing, or that which constitutes it what it is. How the first matter and form were brought into union so as to produce bodies does not appear ; unless nature, the meaning of which term, as employed by Aristotle, it is not easy to apprehend, accomplishes the union.
Aristotle distinguished causes into the material, the formal, the efficient, and the final; the first being that of which things are made, the second that by which they are what they are, the third that by the agency of which anything is produbed, and the last the design of its production. Having thus provided for the existence of substances generally, Aristotle divides them into three classes : the eternal, as the heavens ; the perishable, as the bodies of animals ; and the immu table nature, or prime mover, as it was otherwise called. This prime mover, which occupies the place of God in his system, was considered to be.an eternal, incorporeal, and simple intelligence, and the original source of all motion, being itself unmoved. Its agency extended directly to the first celestial sphere, and mediately through similar inferior intelligences to the lower spheres, and by them to the universe at large.
Sensible bodies were divided by Aristotle into simple and compound ; simple bodies being those elements which result from the combination of primary matter and form, and compound bodies those which proceed from elementary combinations. In bodies thus distinguished there are certain active and passive qualities, which constitute their specific difference, and by which they mutually tend to transform each other into their own nature. In consequence of the action of the first mover, whether direct or indirect, on matter, there is a continual succession of dissolution and reproduction ; reproduction taking place when the essence of a body is entirely changed, and only an augmenta tion or diminution when its accidental qualities undergo mutation.