66

We may take, as examples of this, the problems of the simplest kind, where the principles lay nearest at hand, the mechanical ones. Why," he asks', "do small forces move great weights by means of a lever, when they have thus to move the lever added to the weight? Is it," he suggests, "because a greater radius moves faster?" 66 Why does a small wedge split great weights? Is it because the wedge is composed of two opposite levers?" "Why", when a man rises from a chair, does he bend his leg and his body to acute angles with his thigh? Is it because a right angle is connected with equality and rest?" Why can a man throw a stone further with a sling than with his hand? Is it that when he throws with his hand he moves the stone from rest, but when he uses the sling he throws it already in motion ?" 66 Why, if a circle be thrown on the ground, does it first describe a straight line and then a spiral, as it falls? Is it that the air first presses equally on the two sides and supports it, and afterwards presses on one side more?" Why is it difficult to distinguish a musical note from the octave above? Is it that proportion stands in the place of equality?" It must be allowed that these are very vague and worthless surmises; for even if we were, as some commentators have done, to interpret some of them so as to agree with sound philosophy, we should still be unable to point out, in this author's

1 Mech. Prob. 4.

2 Ib. 18.

3 Ib. 31.

66

6

* Ib. 13.

5

Περι Αψυχα, 11.

6

Περι Αρμον. 14.

works, any clear or permanent apprehension of the general principles which such an interpretation implies.

Thus the Aristotelian physics cannot be considered as otherwise than a complete failure. It collected no general laws from facts; and consequently, when it tried to explain facts, it had no principles which were of any avail.

The same may be said of the physical speculations of the other schools of philosophy. They arrived at no doctrines from which they could deduce, by sound reasoning, such facts as they saw; though they often venture so far to trust their principles as to infer from them propositions beyond the domain of sense. Thus, the principle that each element seeks its own place, led to the doctrine, that, the place of fire being the highest, there is, above the air, a sphere of fire; of which doctrine the word empyrean, used by our poets, still conveys a reminiscence. The Pythagorean tenet that ten is a perfect number', led them to assert that the heavenly bodies are in number ten; and as nine only were known to them, they asserted that there was an antichthon, or counter-earth, on the other side of the sun, invisible to us. Their opinions respecting numerical ratios, led to various other speculations concerning the distances and positions of the heavenly bodies: and as they had, in other cases, found a connexion between proportions of

7 Arist. Metaph.

>

distance and musical notes, they assumed, on this suggestion, the music of the spheres.

Although we shall look in vain in the physical philosophy of the Greek schools, for any results more valuable than those just mentioned, we shall not be surprised to find, recollecting how much an admiration for classical antiquity has possessed the minds of men, that some writers estimate their claims much more highly than they are stated here. Among such writers we may notice Dutens, who, in 1766, published his "Origin of the Discoveries attributed to the Moderns; in which it is shown that our most celebrated Philosophers have received the greatest part of their knowledge from the Works of the Ancients." The thesis of this work is attempted to be proved, as we might expect, by very large interpretations of the general phrases used by the ancients. Thus, when Timæus, in Plato's dialogue, says of the Creator of the world", "that he infused into it two powers, the origins of motions, both of that of the same thing, and of that of different things;" Dutens' finds in this a clear indication of the projectile and attractive forces of modern science. And in some of the common declamation of the Pythagoreans and Platonists, concerning the general prevalence of numerical relations in the universe, he discovers their acquaintance with the law of the inverse square of the distance by which gravitation

8 Tim. 96 a.

9 3d ed.

p. 83.

10

is regulated, though he allows that it required all the penetration of Newton and his followers to detect this law in the scanty fragments by which it is transmitted.

Argument of this kind is palpably insufficient to cover the failure of the Greek attempts at a general physical philosophy; or rather we may say, that such arguments, since they are as good as can be brought in favour of such an opinion, show more clearly how entire the failure was. I proceed now to endeavour to point out its causes.

Sect. 2.-Cause of the Failure of the Greek Physical Philosophy.

THE cause of the failure of so many of the attempts of the Greeks to construct physical science is so important, that we must endeavour to bring it into view here; though the full developement of such subjects belongs rather to the philosophy of induction. The subject must, at present, be treated briefly only.

I will first notice some errors which may naturally occur to the reader's mind, as possible causes of failure, but which, we shall be able to show, were not the real reasons in this case.

The cause of failure was not the neglect of facts. It is often said that the Greeks disregarded experi

10 Ib. p. 88.

ence, and spun their philosophy out of their own thoughts alone; and this is supposed by many to be their essential error. It is, no doubt, true, that the disregard of experience is a phrase which may be so interpreted as to express almost any defect of philosophical method; since the coincidence of all theory with experience is requisite to its truth. But if we fix a more precise sense on our terms, I conceive it may be shown that the Greek philosophy did, in its opinions, recognise the necessity and paramount value of observations; did, in its origin, proceed upon observed facts; and did employ itself to no small extent in classifying and arranging phenomena. We must endeavour to illustrate these assertions, because it is important to show that these steps alone do not necessarily lead to science.

1. The acknowledgment of experience as the main ground of physical knowledge is so generally understood to be a distinguishing feature of later times, that it may excite surprise to find that Aristotle, and other ancient philosophers, not only asserted in the most pointed manner that all our knowledge must begin from experience, but also stated in language much resembling the habitual phraseology of the most modern schools of philosophising, that particular facts must be collected; that from these, general principles must be obtained by induction; and that these principles, when of the most general kind, are axioms. A few passages will show this.