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'admirable author Descartes has treated of at large;. though, for want of sufficient experiments and observa.. tions in natural philosophy, there are some few mia. Itakes in his account of animal nature.
An Illustration of these five Rules by. Similitudes.
THUS we have brought the first part of logic to a!
t conclusion: and it may not be improper here to : represent its excellencies (so far as we have gone) by: general hints of its chief design and use, as well as by: a.various comparison of it to those instruments which mankind have invented for their several conveniences and improvements..
The design of logic is not to furnish us with the pers. ceiving faculty, but only to direct and assist us in the : use of it: it doth not give us the objects of our ideas, but only, casts such a light on those objects which na-. ture furnishes us with, that they may be the more clear.Jy and distinctly known: it doth not add new parts or properties to things, but it discovers the various parts, properties, relations and dependencies of one thing:
izpon another, and by ranking all things under general: , and special heads, it renders the nature, or any of the
properties, powers, and uses 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 illustrate this, it may be : thus represented.
When logic assists us to attain a clear and distinct conception of the nature of things by.definition, it is : like those glasses whereby we behold such objects dis-tinctly, as by reason of their smallness or their great di-. stance appear in confusion to the naked eye : so the telescope discovers to us distant wonders in the heavens, and thews the milky way, and and the bright cloudy spots in a very dark sky to be a collection of little stars, which the eye unaslisted beholds.in mingled.confusion. So when bodies are too small for our light to survey them distinctly, then the microscope is at hand for our aslistance, to fhew. us, all the limbs and features of the most minute animals, with great clearness and distince tion.
II. When we are taught by logic to view a thing completely in all its parts by the help of division, it has the use of an anatomical knife, which diffects an animal. body, and separates the veins, arteries, nerves, muscles, membranes, &*c. and shews us the several parts which: go to the composition of a complete animal. .
III. When logic instructs us to survey an obječ: comprehensively in all the inodes, properties, relations, faces and appearances of it, it is of the fame use as a terrestrial globe, which turning round on its axis represents to us all the variety of land and seas, kingdoms and nations on the surface of the earth in a very short succession of time, shews.the situation and various rela tions of them to each other, and gives a comprehena five view, of them in miniature,
IV. When this art teaches us to distribute any ex tensive idea into its different kinds or species, it may be compared to the prismatic glass, that receives the sun beams or rays of light, which seem to be uniform when: falling upon it, but it separates and diftributes them into their different kinds and colours, and ranks. them. in their proper succeflion.
Or if we descend to fubdivisions and subordinate ranks of being, then distribution may also be said to form the resemblance of a natural tree, 'wherein the genus or general idea. stands for the root or stock, and the several kinds of species, and individuals, are: distributed abroad, and represented in their dependence and connection, like the several boughs, branches, and Jeffer. shoots. For instance, let animal be the root of a. logical tree, the resemblance is seen by mere inspeca
tion, though the root be not placed at the bottom of the page.
The same similitude will serve also to illustrate the division and subdivision of an integral whole, into its feveral parts.
When logic directs us to place all our ideas in a proper method, most convenient both for instruction and memory, it doth the same service as the cases of well contrived shelves in a large library wherein folio's quarto's, octavo's, and leffer volumes, are disposed in such exact order under the particular heads of divinity, history, mathematics, ancient and miscellaneous learning, &c. that the student 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 aslistances as these at hand. in order to manage his conceptions and regulate his ideas, is well prepared to improve his knowledge, and to join those ideas together in a regular manner by judgment, which is the second operation of the mind,', and will be the subject of the second part of logie.
OF FUDGMENT and PROPOSITION.
TUTHEN the mind has got acquaintance with
V things by framing ideas of them, it proceeds to the next operation, and that is, to compare there 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 judge ment; as when we have by perception obtained the ideas of Plato a philosopher, man, innocent, we form these judgments; Plato was a philosopher; no man is innocent.
Some writers have asserted, that judgment consists in a mere perception of the agreement or disagreement of ideas. But I rather think there is an act of the will (at least in most cases) necessary to form a judgment; for though we do perceive or think we perceive ideas to agree or disagree, yet we may sometimes refrain from. judging or affenting to the perception, for fear left the perception should not be sufficiently clear, and we 1hould be mistaken: and I am well ailured at other times, that there are multitudes of judgments formed, and a firm aflent given to ideas joined or disjoined, before there is any clear perception whether they agree or