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XVII. Logie 404. Logie is that important and useful art, which teaches the art of correct thinking. The logicians give five general rules, by which to assist our views in thinking, writing, and speak ing on all subjects.
As these rules are of great and constant use, I have copied them from my owo English Grammar :
a. Conceive of things clearly and distinctly, in their own natures.
Ods. That is, we should acquire a clear and distinct conception of things as they are in their own nature i and not the sontent with obscure and confused ideas, Whey clearer are to be attained,
a. Conceive of things completely, in all their
Obs. - There is a metaphysical, or ideal whale, a na thematical, or integral whole, and a physical, er ewearial whole,
e. Conceive of things comprehensive in all their properties and relations,
Oas-That is, we must consider there is all their modes, attributes, properties, and relations, in order ta attain a compreheasive view of their essential modes ar attributes, and of their various occasional properties, aevidental mades, and relations,
d. Conceive of things extensively, in all their kinds,
098., - That is, we must search out tha various species, or special matutes, which are contained under the subject asa genus ar general malure: as, if we would know the mature of an animal periectly, we mwai tane cognisane of heasts, birds, tislimin, med insects, as well as men i all which are contained under the general nature and me of animal,
e Conceive of things in order, or in a proper nethod.
Oas ---That is, we should rank and place our Ideas la a proper method and just order. We must not conceive of things in a confused heap: but dispose our ideas la some method, which may be easy and useful for the nuderstanding and memory.
400. METHOD is analytical or synthetical, Analytical method resolves the compound into its principles, and the whole into its parts. Synthetical, begins with the parts and leads to a whole, or it puts together the principles and orms a compound.
410. Arguments are either metaphysical, physical, political, moral, mechanical, or theological, according to the science or subject from which they are drawn. The following deserve notice :
a. The Argumentum ad judicium, is an appenl to the common sense of mankind.
è. Tae Argumentum ad fidem, iwan appeal to the faith.
* The Argumentum ad hominem, is an appeal to the practices or professed principles of the adversary
# The Argumentum ad populum, is an appeal to the penple.
e. The Argumentum es concrsun, is when something is proved by means of some proposition previously conrederi,
f. Tar Argumentum ad passiones, is an appeal to the passion
7** rumentima i fartiari, proves the conclusion, hy proving å lexs probable proposition on which the conclusion depends,
A. The irgendw» «marentiam, is founded upon insuficient principles, which the opponent has not kill to refute.
i, Argumentum ad verecundium, bs drawn from autho, rity we are ashamed to dispute,
. A direct argument is that which immediately proves the proposition in question,
I. An indirect argument proves the conelusion , hy proving or disproving some proposition upon whien the conelusion depends,
411, Crrtainty or Truth is of several kinds : there is a mathematical certainty, which admits of demonstration : a moral certainty, which is derived from testimony: a physical certainty, derived from the evidence of the senses and the course of nature; and a theological eertainty, founded on the doctrines of the Scriptures,
412. Evidence is of different kinds; as the evidence of sense, founded on the perceptions of our senses.
The evidence of intuition, founded on selfevident axioms; as that the whole is greater than a part, or, every eflect is produced by some cause,
The evidence of reason, founded on clear and indubitable deductions from well-founded premises and doctrines,
And the evidence of faith, deduced from the testimony of others,
413. Demonstrations are a succession of con. nècied Propositions, beginning with self evident truths and advancing to remoter ones,
A Demonstration á priori, is when the effect is proved by referring to the cause,
A Demonstration à posteriori, is when the cause is inferred from the effects,
Obs-Corollaries are sell-evident inferences from e* tablislied propositione,
414. Sophistry is false reasoning, founded ou false premises, or on ambiguity of terms.
Obs.--As most of the evils which exist in society grow out of sophistry, no art is more important than that which enables us to detect or expose it. The crimes of courts and wicked ministers usually escape punishment, fram the effect of sophistry ; and there would be few or no wara, if sophistry did not triumph in the statements of the parties,
A Sophism of Composition, is when we infer that of any thing in an aggregate or compounded sense, which is only true in a divided sense.
A Sophism of division, is when we infer any thing in a divided sense, which is only true in a compounded sense.
A Sophism of equivocation, is when we use words of an ambiguous or double sense, and draw inferences in one sense, of which the proposition is capable only in the other,
415. A pelitio principii, or begging the question, is the supposition of what is not granted, or a supposed proof, by stating the question in other words.
The reductio ad absurdum, is when the truth of a proposition is proved by shewing the absurdity of a contrary supposition.
416. Induction consists in distributing a general idea into its species, and aseribing to the whole the property found in the species.
A false induction is when general deductions are made from son limited a number of experiments or facts. The fallacia acordantis, is when we draw in
ferences in regard to the nature of a thing, from circumstances only temporary or accidental,
The ignorantia elenchi, is a mistake of the question, or when one thing is proved instead of another.
Analogy is an argument in which, fronta enttesponding causes, are deduced corresponding effecte.
O'The sources of errors are, (1.) The want wf 4i11. gence in investigation. (2.) Judging of things by their enternal appearance only. (3.) Not separating the gnod and bad qualities thai perverletlie same thing, but forming hasty judgment. (4.) Comparing things with our own sittation in life ; or as they happen to affert we. (5.) Associating an idea with something disagreeable, of the contraty. (6.) Prejudices formed in our infancy. (11) Giving credit to the assertions of miste preventatione of others, without inquiring into their motives, 99 in newe-writers and reviewers; and (5.) Subtnitting to the furee and influence of custom and fashion.
417. A Syllogismi is a sentence made up of three propositions, so disposed, as that the last is necessarily inferred from those that precede it.
Every Syllogism contains two premises and a conclusion; or a major and minor proposition and a consequence.
Example of a Syllogism : Major. • * Our Creatur ought to be worshipped. Minor God is our Creator. Coneguence. Therefore Gud ought to be worshipped, 410. An Argument is a series of syllogisme : and, although argutente do not retain their syllogistic form in ordinary discourse, yet all miyuments may be reduced to syllogisms; and errors or sophismo may thus be detected,