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ery grammar. Adair's Questions render it practical for schools.
XVII. Logic. 417. Logic 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 speaking on all subjects.
As these rules are of great and constant use, I have copied them from my own English Grammar:
a. Conceive of things clearly and distinctly, in their own natures.
Obs.-That is, we should acquire a clear and distinct conception of things as they are in their own nature ; and not be content with obscure and confused ideas, when clearer are to be attained.
b. Conceive of things completely, in all their parts.
Obs—There is a metaphysical or ideal whole, a mathematical or integral whole, and a physical or essential whole.
c. Conceive of things comprehensively, in all their properties and relations.
Obs.—That is, we must consider them in all their modes, attributes, properties, and relations ; in order to attain a comprehensive view of their essential modes or attributes, and of their various occasional properties, accidental modes, and re. lations.
d. Conceive of things extensively, in all their kinds.
Obs. That is, we must search out the various species, or special natures, which are contained under the subject as a genus or general nature : as, if we would know the nature of an animal perfectly, we must take cognizance of beasts, birds, fishes, and insects, as well as men; all which are contained under the erul nature and name of aniinal.
e. Conceive of things in order, or in a proper method.
Obs. That is, we should rank and place our ideas in a proper method and just order. We must not conceive of things in a confused heap: but dispose our ideas in some method, which may be easy and useful for the understanding and memory.
418. 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 forms a compound.
419. 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 appeal to the common sense of mankind.
b. The Argumentum ad fidem, is an appeal to the faith.
c. The Argumentum ad hominem, is an appeal to the practices or professed principles of the adversary.
d. The Argumetum ad populum, is an appeal to the people.
e. The Argumentum ex concesso, is when something is prov. ed by means of some proposition previously conceded.
f. The Argumentum ad passiones, is an appeal to the passions.
g. The Argumentum a fortiori, proves the conclusion, by proving a less probable proposition on which the conclusion depends.
h. The Argumentum ad ignorantiam, is founded upon insufficient principles, which the opponent has not skill to refute.
i. Argumentum ad verecundium, is drawn from authority we are ashamed to dispute.
k. A direct argument is that which immediately proves the proposition in question.
1. An indirect argument proves the conclusion, by proving or disproving some proposition upon which the conclusion depends.
420. Certainty 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 certainty, founded on the doctrines of the Scriptures.
421. Evidence is of different kinds; as the evidence of sense, founded on the perceptions of our senses.
The evidence of intuition, founded on self-evident axioms; as that the whole is greater than a part, or, that
every effect is produced by some cause. The evidence of reason, founded on clear and in
dubitable deductions from well-founded premises and doctrines.
And the evidence of faith, deduced from the testimony of others.
422. Demonstrations are a succession of connected propositions, beginning with self-evident truths and advancing to remoter ones.
A Demonstration a priori, is when the effect is proved by referring to the cause.
A Demonstration a posteriori, is when the cause is inferred from the effects.
Obs.--COROLLARIES are self-evident inferences from established propositions.
423. Sophistry is false reasoning, founded on 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, from the effect of sophistry; and there would be few or do wars, 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.
424. A petitio 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.
425. Induction consists in distributing a general
idea into its species, and ascribing to the whole the property found in the species.
Å false induction, is when general deductions are made from too limited a number of experiments or facts.
The fallacia accidentis, is when we draw inferences 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, from corresponding causes, are deduced corresponding effects.
Obs.--The sources of errors are, (1.) The want of diligence in investigation. (2.) Judging of things by their external appearances only. (3.) Not separating the good and bad qualities that pervade the same thing, but forming a hasty judg. ment. (4.) Comparing things with our own situation in life ; or as they happen to affect us. (5.) Associating an idea with something disagreeable, or the contrary. (6.) Prejudices formed in our infancy. (7) Giving credit to the assertions or misrepresentations of others, without inquiring into their motives, as in news-writers and reviewers; and (8.) Submitting to the force and influence of custom and fashion.
426. A Syllogism 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 a minor proposition and a consequence.
Example of a Syllogism :
427. An Argument is a series of syllogisms; and, although arguments do not retain their syllogistic form in ordinary discourse, yet all arguments may be reduced to syllogisms; and errors or sophisms may thus be detected.
428. Formerly Logic, or the art of reasoning, was almost the sole business of a university education ;
but it is now in some degree superseded, by the practice of reasoning in the study of mathematics, by the various branches of philosophy, and by the perusal of the classic authors.
Obs. The great master of philosophy, Aristotle, divided all science into Theorems formed of Syllogisms, which Syllogišms were composed of Propositions, which propositions. were formed of terms; which terms were Words or Sigris of our Ideas of Things. He then considered all things with re. ference to their Ten Categories, or Predicaments; as Substance, Quality, Quantity, Relation, Action, Passiveness, When, Where, Position, and Habit.
XVIII. Rhetorica 429. Rhetoric teaches us to affèet the passions by suitable illustrations and imagery; and to arrange our arguments to the best advantage, so as to make the deepest impressions on the feelings and judgment of those whom we address.
430. The following are the chief figures of speech.
a. Simile or comparison, is that figure by which we compare one thing with another for the sake of illustration.
b. Metaphor, is a comparison expressed without the signs of comparison; as, when we say of a minister, that he is the pillar of the state, we speak in metaphor; and when we say, that Charles the Twelfth. was the lion of the north, we speak metaphorically.
c. Allegory, is a continuation of several metaphors, so connected as to form a kind of parable or fable ; as, in describing the people of Israel under the image of a vine.
d. Irony, is a figure in which we urge one thing, and mean the contrary, in order to give effect to our meaning; as, in describing a notorious cheat, we say, ironically, A mighty honest man truly !
e. Hyperbole, gives us the highest idea of an object, and magnifies it beyond its natural dimensions; as, Achilles was swifter than a stag.