'' upon the whole. Habit of a different kind has an influence no lefs powerful. Persons who are in the habit of reasoning, require demonstration for every thing: even a felf-evident propofition is not fuffered to escape. Such demonftrations occur more than once in the Elements of Euclid, nor has Ariftotle, with all his fkill in logic, entirely avoided them. Can any thing be more felf-evident, than the difference between pleasure and motion? Yet Aristotle attempts to demonftrate, that they are different. No mo"tion," fays he, except circular mo<< tion, is perfect in any one point of "time; there is always fomething want"ing during its courfe, and it is not per"fected till it arrive at its end. But plea"fure is perfect in every point of time; "being the fame from the beginning to "the end." The difference is clear from perception but instead of being clear from this demonftration, it fhould rather follow from it, that pleasure is the fame with motion in a circle. Plato also attempts to demonftrate a felf-evident propofition, that a quality is not a body. "Every body," fays he, " is a fubject: quality : 66 "quality is not a fubject, but an accident; ergo, quality is not a body. Again, A body cannot be in a fubject: every quality is in a fubject; ergo, qua 66 lity is not a body." But Defcartes affords the moft illuftrious inftance of the kind. He was the greatest geometer of the age he lived in, and one of the greatest of any age; which infenfibly led him to overlook intuitive knowledge, and to admit no propofition but what is demonstrated or proved in the regular form of fyllogifm. He took a fancy to doubt even of his own existence, till he was convinced of it by the following argument. Cogito, ergo fum: I think, therefore I exift. And what fort of a demonftration is this after all? In the very fundamental propofition he acknowledges his existence by the term I; and how abfurd is it, to imagine a proof neceffary of what is admitted in the fundamental propofition? In the next place, How does our author know that he thinks? If nothing is to be taken for granted, an argument is no less neceffary to prove that he thinks, than to prove that he exifts. It is true, that he has intuitive knowledge of his thinking; but has he not not the fame of his exifting? Would not a man deserve to be laughed at, who, after warming himself at a fire, should imagine the following argument necessary to prove its existence, "The fire burns, ergo "it exifts?" Listen to an author of high reputation attempting to demonftrate a felf-evident propofition. "The labour of "B cannot be the labour of C; because it "is the application of the organs and powers of B, not of C, to the effecting "of fomething; and therefore the labour "is as much B's, as the limbs and faculties made use of are his. Again, the effect or produce of the labour of B, is not the "C effect of the labour of C: and therefore "this effect or produce is B's, not C's; as much B's, as the labour was B's, and 66 not C's: Because, what the labour of "B caufes or produces, B produces by "his labour; or it is the product of B by his labour: that is, it is B's product, not C's or any other's. And if C fhould pretend to any property in that which B can truly call his, he would act contrary to truth (a)." In every fubject of reafoning, to define (a) Religion of Nature delineated, fect. 6. parag. 2. VOL. III. P P terms terms is neceffary in order to avoid miftakes and the only poffible way of defining a term, is to exprefs its meaning in more fimple terms. Terms expreffing ideas that are fimple without parts, admit not of being defined, because there are no terms more fimple to exprefs their meaning. To say that every term is capable of a definition, is in effect to say, that terms resemble matter; that as the latter is divifible without end, fo the former is reducible into fimpler terms without end. The habit however of defining is fo inveterate in some men, that they will attempt to define words fignifying fimple ideas. Is there any neceffity to define motion: do not children understand the meaning of the word? And how is it poffible to define it, when there are fimple to define it by? attempts that bold tafk. 66 not words more Yet Worster (a) "A continual change of place," fays he, or leaving "one place for another, without remain"ing for any space of time in the fame "place, is called motion." That every body in motion is continually changing place, is true but change of place is not (a) Natural Philosophy, p. 31. motion; motion; it is the effect of motion. Gravefend (a) defines motion thus, "Motus eft tranflatio de loco in locum, five con"tinua loci mutatio*;" which is the fame with the former. Yet this very author admits locus or place to fignify a simple idea, incapable of a definition. Is it more fimple or more intelligible than motion? But, of all, the most remarkable definition of motion is that of Aristotle, famous for its impenetrability, or rather abfurdiActus entis in potentia, quatenus in potentia +." His definition of time is numerus motus fecundum prius ac pofterius. This definition as well as that of motion, may more properly be confidered as riddles propounded for exercifing invention. Not a few writers on algebra define negative quantities to be quantities lefs than nothing. ty, Extenfion enters into the conception of every particle of matter; because (a) Elements of Phyfics, p. 23. every * "Motion is, the removing from one place to "another, or a continual change of place." "The action of a being in power, fo far às it is "in power." |