turn us out of the beaten track.

An ancient maxim of the once celebrated Thomas Aquinas -Cave ab illo qui unicum librum legit, deserves to be considered by all those, who dare not venture abroad in quest of truth, but behind the back of their tutor: in which fituation they may possibly see so much of him, as to be able to see nothing else.

It will readily be granted, I suppose, that such a practice as this is very childish and absurd, provided the observation be applied only to the prejudices which once reigned in favour of Aristotle, Descartes, or the Chymists yet it so happens, that if an author comes home to his own times, and ventures to look into any of the pretensions of the present age, he is in danger of being assaulted by all that meet with him, and generally with the greatest vehemence by those who are the most superficial in their knowledge.

This consideration, I frankly confess, hath , sometimes had so much weight, and appear

ed so formidable to me, that I have been almost tempted to throw my pen into the fire, rather than employ it against any current opinion. A sincere love, however, of the science of nature, and a confirmed persuasion both of its usefulness and its im

portance,

portance, ought to prevail against these difficulties; and they have prevailed with me, to try, in the first place, if I can dispel some of that learned darkness with which the subject has been overspread, and open the way to a better understanding of it.

And here I cannot but reckon it a great advantage to truth, though it is none at all to myself, that, in perusing the following sheets, the reader is in no danger of being dazzled or misled by the influence of a name. so inconsiderable as that of the author; who has no popular prejudices to appeal to, and cannot expect to be heard upon any considerations, but the importance of the matter, the clearness of the facts, and the strength of the arguments he has to propose.

Why this attempt should give offence to any person, he cannot well imagine. For, if we divide the world of Philosophers into two parties, some of whom are influenced by an undissembled zeal for the Christian faith, while others are not ashamed to declare that they have no religion at all; the former, I presume, can have no good objection to any phyfical disquisition, which is conducted. with submission and modesty; it being impossible that true religion and true philosophy

should be at variance; because He who created all those works, which are the proper objects of natural philosophy, was also the author of divine revelation: and God is not divided against himself. And unless it were in my power to point out some particulars, in which this disquisition may prove to be of service to religion, I should be able to give but a poor account of those many hours, which I have been obliged to borrow from that profession and study, to which the providence of God hath more immediately called me. As to the latter, they, I think, who are so forward to tell us, they have rejected all human authority, and can think freely in matters of religion, will not be very consistent with themselves, if they are angry with me for thinking as freely in matters of philosophy.

This ought to be remembered likewise for the satisfaction of all parties, that if the method of explaining natural effects, now in vogue amongst us, be established on sufficient proof, or rather, as it is commonly reported, on undeniable demonstration; all that I shall occasionally offer against it, though it may puzzle some superficial readers unacquainted with the subject, will not

weaken

weaken it in the opinion of any man of true learning and judgment. If it be not established on sufficient proof, what harm will there be in disbelieving it? We shall then be at liberty to turn our thoughts another way, and may be looking out with some better prospect of success. And as it appears, to me at least, that no physical effect is really explained or understood, unless it is deduced from a physical cause, the existence and operation of which can be experimentally demonstrated; I shall humbly endeavour to shew, that the modern philosophy, although it has carried natural knowlege to a great height in some respects, can furnish no sound arguments or real objections against the mechanism of the natural world; and that in every thing it has advanced against this mechanism, it doth itself proceed upon such principles as are arbitrary, and unsupported by any evidence that is truly philosophical or physical. These I know are very bold assertions; but if the reader will only prevail with himself to bear with me for a while, and have a little patience, he may perhaps find some reasons, more considerable than he is aware of, for being of the same opinion.

Every person, who makes use of his senses, must needs be convinced, that the matter comprehended within this visible world is full of motion; and the learned have very greatly doubted, by what means, and after what manner, this motion is supported and preserved. Some of them, according to their own accounts, begin with the two principles of matter and a void space. To their matter they give this capital Law, that if once moved, it shall continue in motion, because it has no power to stop itself. Thus they elude the necessity of providing any physical cause for the conservation of motion, and save themselves all that trouble, which they might otherwise have in searching after it. Then, from the principle of a vacuum, or space void of all sensible matter, they propose the two following advantages; that a body will have room wherein to move, and that being once set a going, there will be nothing in the way to obstruct or diminish the quantity of its motion.

In this manner they account for the continuance of that motion which is rectilinear: but then for the producing of other motion in curves and compounded directions, with which nature is observed very much to

abound,