that we may know when to expect them, or how to bring them CHAP. VI. about. This is very often of real importance in life; and this purpose is ferved, by knowing what, by the course of nature, goes before them and is connected with them; and this, therefore, we call the cause of fuch a phænomenon.

If a magnet be brought near to a mariner's compass, the needle, which was before at reft, immediately begins to move, and bends its courfe towards the magnet, or perhaps the contrary way. If an unlearned failor is afked the cause of this motion of the needle, he is at no lofs for an answer. He tells you it is the magnet; and the proof is clear; for, remove the magnet, and the effect ceafes; bring it near, and the effect is again produced. It is, therefore, evident to fenfe, that the magnet is the cause of this effect.

A Cartefian Philofopher enters deeper into the cause of this phænomenon. He obferves, that the magnet does not touch the needle, and therefore can give it no impulfe. He pities the ignorance of the failor. The effect is produced, fays he, by magnetic effluvia, or fubtile matter, which paffes from the magnet to the needle, and forces it from its place. He can even fhew you, in a figure, where thefe magnetic effluvia iffue from the magnet, what round they take, and what way they return home again. And thus he thinks he comprehends perfectly how, and by what cause, the motion of the needle is produced.

A Newtonian Philofopher enquires what proof can be offered for the existence of magnetic effluvia, and can find none. He therefore holds it as a fiction, a hypothesis; and he has learned that hypothefes ought to have no place in the philofophy of naHe confeffes his ignorance of the real caufe of this motion, and thinks, that his business, as a Philofopher, is only to find from experiment the laws by which it is regulated in all cafes.

ture.

Thefe

CHAP. VI.

Thefe three perfons differ much in their fentiments with regard to the real cause of this phænomenon; and the man who knows most is he who is fenfible that he knows nothing of the matter. Yet all the three speak the same language, and acknowledge, that the cause of this motion is the attractive or repulfive power of the magnet.

What has been faid of this, may be applied to every phænomenon that falls within the compass of natural philofophy. We deceive ourselves, if we conceive, that we can point out the real efficient cause of any one of them.

The grandeft discovery ever made in natural philofophy, was that of the law of gravitation, which opens fuch a view of our planetary fyftem, that it looks like fomething divine. But the author of this difcovery was perfectly aware, that he discovered no real caufe, but only the law or rule, according to which the unknown cause operates.

Natural Philofophers, who think accurately, have a precise meaning to the terms they use in the science; and when they pretend to shew the cause of any phænomenon of nature, they mean by the cause, a law of nature of which that phænomenon is a neceffary confequence.

The whole object of natural philofophy, as NEWTON expressly teaches, is reducible to these two heads; firft, by juft induction from experiment and obfervation, to discover the laws of nature, and then to apply thofe laws to the folution of the phænomena of nature. This was all that this great Philosopher attempted, and all that he thought attainable. And this indeed he attained in a great measure, with regard to the motions of our planetary system, and with regard to the rays of light.

But fuppofing that all the phænomena that fall within the

reach

reach of our fenfes, were accounted for from general laws of na- CHAP. VI. ture, justly deduced from experience; that is, supposing natural philosophy brought to its utmost perfection, it does not difcover the efficient cause of any one phænomenon in nature.

The laws of nature are the rules according to which the effects are produced; but there must be a cause which operates according to these rules. The rules of navigation never navigated a fhip. The rules of architecture never built a house.

Natural philofophers, by great attention to the course of na-ture, have discovered many of her laws, and have very happily applied them to account for many phænomena; but they have never discovered the efficient caufe of any one phænomenon ;. nor do those who have diftinct notions of the principles of the fcience, make. any fuch pretence.

Upon the theatre of nature we fee innumerable effects, which require an agent endowed with active power; but the agent is behind the scene. Whether it be the Supreme Cause alone, or a. fubordinate caufe or causes; and if fubordinate caufes, be em-ployed by the Almighty, what their nature, their number, and their different offices may be, are things hid, for wife reasons. without doubt, from the human eye.

It is only in human actions, that may be imputed for praise or blame, that it is, neceffary for us to know who is the agent ; and in this, nature has given us all the light that is necessary for: our.conduct.

CHA P.

CHAP. VIL

E

CHA P. VII.

Of the Extent of Human Power.

VERY thing laudable and praife-worthy in man, muft confift in the proper exercise of that power which is given him by his Maker. This is the talent which he is required to occupy, and of which he must give an account to him who committed it to his truft.

To fome perfons more power is given than to others; and to the fame perfon more at one time and less at another. Its existence, its extent, and its continuance, depend folely upon the pleasure of the Almighty; but every man that is accountable. must have more or lefs of it. For, to call a perfon to account, to approve or disapprove of his conduct, who had no power to do good or ill, is abfurd. No axiom of Euclid appears more evident than this.

As power is a valuable gift, to under-rate it is ingratitude to the giver; to over-rate it, begets pride and presumption, and leads to unfuccefsful attempts. It is therefore, in every man, a point of wisdom to make a just estimate of his own power. Quid ferre recufent, quid valeant humeri.

We can only speak of the power of man in general; and as our notion of power is relative to its effects, we can eftimate its extent only by the effects which it is able to produce.

It would be wrong to estimate the extent of human power by the effects which it has actually produced. For every man had power to do many things which he did not, and not to do many

things

things which he did; otherwife he could not be an object either CHAP. VII. of approbation or of disapprobation, to any rational being.

The effects of human power are either immediate, or they are

more remote.

The immediate effects, I think, are reducible to two heads. We can give certain motions to our own bodies; and we can give a certain direction to our own thoughts.

Whatever we can do beyond this, must be done by one of thefe means, or both.

We can produce no motion in any body in the universe, but by moving firft our own body as an inftrument. Nor can we produce thought in any other perfon, but by thought and motion in ourselves.

Our power to move our own body, is not only limited in its extent, but in its nature is fubject to mechanical laws. It may be compared to a spring endowed with the power of contracting or expanding itself, but which cannot contract without drawing equally at both ends, nor expand without pushing equally at both ends; fo that every action of the fpring is always accompanied with an equal reaction in a contrary direction.

We can conceive a man to have power to move his whole body in any direction, without the aid of any other body, or a power to move one part of his body without the aid of any other part. But philosophy teaches us that man has no fuch power.

If he carries his whole body in any direction with a certain quantity of motion, this he can do only by pushing the earth, or fome other body, with an equal quantity of motion in the contrary

G