admirable author Defcartes has treated of at large; though, for want of fufficient experiments and obferva-tions in natural philofophy, there are fome few miftakes in his account of animal nature. SECT. XIII. An Illuftration of these five Rules by Similitudes. HUS we have brought the first part of logic to a T conclufion and it may not be improper here to reprefent its excellencies (fo far as we have gone) by general hints of its chief defign and use, as well as by a various comparison of it to those inftruments which mankind have invented for their feveral conveniences and improvements.. The defign of logic is not to furnish us with the per-ceiving faculty, but only to direct and affift us in the: ufe of it: it doth not give us the objects of our ideas,. but only, cafts fuch a light on thofe objects which nature furnishes us with, that they may be the more clear-ly and diftinctly known: it doth not add new parts or properties to things, but it discovers the various parts,. properties, relations and dependencies of one thing. upon another, and by ranking all things under general and fpecial heads, it renders the nature, or any of the properties, powers, and ufes of a thing more easy to be found out, when we seek in what rank of beings it lies, and wherein it agrees with, and wherein it differs: from others. If any comparisons would illuftrate this, it may be thus reprefented. When logic affifts us to attain a clear and diftinct conception of the nature of things by definition, it is: like thofe glaffes whereby we behold fuch objects dif-tinctly, as by reafon of their smallness or their great diftance appear in confufion to the naked eye: fo the telescope difcovers to us diftant wonders in the heavens,, and thews the milky way, and and the bright cloudyspots in a very dark sky to be a collection of little stars, which the eye unaffited beholds in mingled confufion. So when bodies are too fmall for our fight to furvey them diftinctly, then the microfcope is at hand for our affiftance, to fhew us all the limbs and features of the moft minute animals, with great clearness and diftinc tion. II. When we are taught by logic to view a thing completely in all its parts by the help of divifion, it has the ufe of an anatomical knife, which diffects an animal. body, and separates the veins, arteries, nerves, muscles, membranes, &c. and fhews us the feveral parts which go to the compofition of a complete animal. III. When logic inftructs us to survey an object: comprehensively in all the modes, properties, relations, faces and appearances of it, it is of the fame ufe as a terreftrial globe, which turning round on its axis reprefents to us all the variety of land and feas, kingdoms and nations on the furface of the earth in a very short fucceffion of time, fhews the fituation and various relations of them to each other, and gives a comprehen five view of them in miniature. IV. When this art teaches us to diftribute any extensive idea into its different kinds or fpecies, it may be compared to the prismatic glafs, that receives the fun beams or rays of light, which feem to be uniform when falling upon it, but it feparates and diftributes them into their different kinds and colours, and ranks them in their proper fucceffion.. Or if we defcend to fubdivifions and fubordinate ranks of being, then diftribution may also be faid to form the resemblance of a natural tree, wherein the genus or general idea ftands for the root or stock, and the feveral kinds of fpecies, and individuals, arediftributed abroad, and reprefented in their dependence, and connection, like the feveral boughs, branches, and leffer fhoots. For inftance, let animal be the root of a logical tree, the refemblance is seen by mere infpec tion, though the root be not placed at the bottom of the page. The fame fimilitude will ferve also to illuftrate the divifion and fubdivifion of an integral whole, into its feveral parts.. When logic directs us to place all our ideas in a proper method, moft convenient both for instruction and memory, it doth the fame fervice as the cafes of well contrived fhelves in a large library wherein folio's 'quarto's, octavo's, and leffer volumes, are difpofed in fuch exact order under the particular heads of divinity, history, mathematics, ancient and miscellaneous learning, &c. that the ftudent knows where to find every book, and has them all as it were within his command at once, because of the exact order wherein they are placed. The man who has fuch affistances as thefe at hand. in order to manage his conceptions and regulate his ideas, is well prepared to improve his knowledge, and to join thofe ideas together in a regular manner by judgment, which is the fecond operation of the mind,', and will be the fubject of the fecond part of logie. THE SECOND PART OF LOGI C Of JUDGMENT and PROPOSITION. WH HEN the mind has got acquaintance with to the next operation, and that is, to compare these ideas together, and to join them by affirmation, or difjoin them by negation, according as we find them to agree or difagree. This act of the mind is called judgment; as when we have by perception obtained the ideas of Plato a philofopher, man, innocent, we form these judgments; Plato was a philofopher; no man is inno cent. Some writers have afferted, that judgment confifts in a mere perception of the agreement or difagreement of ideas. But I rather think there is an act of the will (at least in moft cafes) neceffary to form a judgment;. for though we do perceive or think we perceive ideas to agree or difagree, yet we may fometimes refrain from. judging or affenting to the perception, for fear left the perception fhould not be fufficiently clear, and we Thould be mistaken: and I am well affured at other times, that there are multitudes of judgments formed, and a firm affent given to ideas joined or disjoined, before there is any clear perception whether they agree or |