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question concerning the production of the visible world: and he proposed a third scheme, which has also had its share of popularity. According to this remodelled plan, the sensible universe is the result of four distinct principles,-intelligence, matter, form, and privation; which last term is little more than a mere synonym for space or vacuum; and thus far the theory of Aristotle chiefly differs from that of Plato, by interweaving into it his fourth principle, derived from Democritus, and the other Atomic philosophers, and which he seems to have added to it with a view of providing a proper theatre for the two principles of form and matter to move in. He supposes all these to have equally existed from eternity; and the last three to have been eternally acted upon or thrown into a definite series of motions, upon which alone the existence and harmony of things are dependent, by the immutable and immaterial principle of intelligence, whose residence he places in the purest and loftiest sphere or circle of the heavens: a sphere that in its vast embrace comprehends ten lower or subordinate spheres, that lie between itself and the earth, which forms the centre of the whole; and, in conjunction with the earth, constitutes the universal world.

This supreme intelligence Aristotle conceived to be in himself for ever at rest; and the tranquil and peaceable sphere in which he resides he denominated the empyreum or heaven of bliss. But though enjoying eternal rest himself, he communicates motion, necessarily and essentially, upon this theory, to the sphere immediately below him; as this, in its turn, communicates it in different directions, and with different velocities, to the other spheres that

revolve within its range*; whence the sphere thus earliest receiving motion, and nearest to the empyreum, Aristotle denominated the PRIMUM MOBIle, or first moving power: it constituted the tenth in the regular series; the ninth, or that which lies next to it, being denominated the crystalline heavens ; the eighth, the starry sphere, or heavens; and the remaining seven deriving their names from, and being appropriated to, the different revolutions of the different planets, as Saturn, Jupiter, Mars, Apollo or the sun, Venus, Mercury, and Diana or the moon the earth, forming the centre of the whole, being an imperfect sphere, with a larger proportion of matter at the equator; on which account the earth was conceived to turn on her axis in an alternating or rocking motion, revolving round the axis of the ecliptic, and making the stars appear to shift their places at the rate of about one degree in seventy-two years. According to this calculation, all of them would appear to perform a complete revolution in the space of 25,920 years, and, consequently, to return to the precise situation they occupied at the commencement of such period. This period was hence denominated the ANNUS MAGNUS, or GREAT YEAR, and not unfrequently the PLATONIC YEAR, as the same kind of revolution was in some measure taught also by Plato.

The motory power, thus impressed by the intelligent moving principle, not voluntarily but by necessity, upon the different heavenly spheres, and finally upon the earth, and productive of that catenation of effects which is equally without beginning and

* Diog. Laert. lib. v. sect. 23. Arist. Phys. lib. i. cap. 3, 4. De Cæl. lib. ii. cap. 3. 11.

without end, Aristotle denominated NATURE, and thus furnished us with a word, which has for ages been so extensively made use of, that, though there is nothing in all language more imprecise, there is nothing we could spare with more inconvenience. The same term, indeed, is occasionally employed by Plato, but in a sense still less definite if possible, and at the same time still less comprehensive.

On the revival of literature, this theory, together with the other branches of Peripatetic science, was chiefly restored and studied; and continued, indeed, to be generally adhered to for upwards of a century after the publication of the Copernican system; which is well known to have at first experienced but a very cold and inhospitable reception from the literary world. And it is hence this theory that is principally adverted to and described in the productions of all the early poets as well as philosophers of every part of modern Europe. And so complete was the triumph of the Peripatetic school in all its doctrines throughout Christendom, at this period, that Melancthon makes it a matter of complaint that, even in the sacred assemblies, parts of the writings of Aristotle were read to the people instead of the Gospel. Even Milton himself, though born considerably more than a century after Copernicus, wavers as to the propriety of adopting his hypothesis of the heavens, and hence, in his Paradise Lost*, leaves it doubtful which of the two, the new or the old, ought to be preferred. The best and most splendid description of the Aristotelian theory that I have ever met with is contained in the Lusiad

* Book viii.

of Camoens: the whole is too long for quotation, but I cannot doubt that you will be pleased with the following lines from Mr. Mickle's very spirited version of the Portuguese bard, as delineating the different heavenly spheres that were supposed to lie one within another, like the different tunics of an onion :

These spheres behold: the first in wide embrace
Surrounds the lesser orbs of various face;
The EMPYREAN this, the holiest heaven,
To the pure spirits of the blest is given:
No mortal eye its splendid rays may bear,
No mortal bosom feel the raptures there.
The earth, in all her summer pride array'd,
To this might seem a dark sepulchral shade.
Unmoved it stands.-Within its shining frame,
In motion swifter than the lightning's flame,
Swifter than sight the moving parts may spy,
Another sphere whirls round its rapid sky:
Hence MOTION darts its force, impulsive draws,
And on the other orbs impresses laws.*

These hypotheses are abstruse, and perhaps ill calculated to afford amusement; but in a course of physical study they ought by no means to be overlooked. Abstruse as they are, the one or the other of them is interwoven with the whole range of classical literature, and, as I have already remarked, held the ascendant in the horizon of metaphysics till within the last two centuries; and I have dwelt upon them the rather, because, much as we still hear of them, and find them adverted to in books, I am not acquainted with any work whatever that gives any thing like a clear and intelligible summary of their principles. Their more prominent defects *Book x. p. 443. 4to. 1776.

are, in few words, as follows: Independently of conveying very imperfect and erroneous views of the creation, they equally concur in reducing matter, notwithstanding its pretended eternal existence, to a nonentity, and confound its properties with those of pure intelligence, by giving to numbers, ideas, or a mere abstract notion, real form and existence. The most powerful advocate of the Platonic theory, in modern times, was the very excellent Bishop Berkeley; who, in the true spirit of consistency, and with a boldness that no consequences could deter, openly denied the existence of a material world, and thus reduced the range of actual entities from three to two, an intelligent first cause, and intellectual forms or ideas, and gave the death-blow to the system by avowing its necessary result.

In modern times, however, the infinite divisibility of matter has for the most part been supported upon different grounds, and philosophers have involved themselves in the same fatal consequences, by a much shorter process of reasoning. No compound or visible bodies, it is well known, ever come into immediate contact with each other, or influence each other by means of simple solidity. The earth is affected by the sun, the moon by the earth; the waters of the earth by the moon. Light is reflected from substances to which it directs its course, at a distance, and without impinging upon them. The particles of all bodies deemed the most solid and impermeable, are capable of approaching nearer, or receding farther from each other, by an application of different degrees of cold or heat. We can, hence, it is said, form no conception of perfect solidity; and every

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