« ForrigeFortsæt »
former times. This made the Emperor Marcus Antonius to say, “ By looking back into history, and considering the fate and revolutions of governments, you will be able to form a guess, and almost prophesy upon the future. For things past, present, and to come, are strangely uniform, and of a colour, and are commonly cast in the same mould. So that upon the matter, forty years of human life may serve for a sample of ten thousand." Collier's Antonius, Book VII. sect. 50.
7. There are also some other principles of judging conceraing the past actions of men in former ages, besides books, bistories and traditions, which are the mediums of conveying buman testimony; as we may infer the skill and magnificence of the ancients by some fragments of their statues, and ruins of their buildings. We know what Roman legions came into Great Britain, by numbers of bricks dug out of the earth in some parts of the island, with the marks of some particular legion upon them, which must have been employed there in brickmaking. We rectify some mistakes in history by statues, coins, old altars, utensils of war, &c. We confirm or disprove some pretended traditions and historical writings, by medals, images, pictures, urns, &c.
Thus I have gone through all those particular objects of our judgment which I first proposed, and bave laid dowo prid. ciples and rules by which we may safely conduct ourselves therein. There is a variety of other objects, concerning which we are occasionally called to pass a judgment, namely, the characters of persons, the value and worth of things, the sense and meaning of particular writers, matters of wit, oratory, poesy, njatters of equity in judicial courts, matters of tratlie and commerce between man and man, which would be endless to enumerate. But if the general and special rules of judgment, which have been mentioned in these two last chapters, are treasured up in the mind, and wrought into the very temper of our souls in our younger years, they will lay a foundation for just and regular judgment concerning a thousand special occurrences in the religious, civil, and learned life.
THE THIRD PART OF LOGIC,
Of Reasoning and Syllogism. AS the first work of the mind is perception, whereby our ideas are framed, and tbe second is judgment, which joins or disjoins our ideas, and forms a proposition, so the third opera, tion of the mind is reasoning, which joins several propositions together, and makes a syllogism, that is," an argument where by we are wont to imfer something that is less known, from truths which are more evident."?
In treating of this subject, let us consider more particularly,
1. The nature of a syllogism, and the parts of which it is composed. 2. The several kinds of syllogisms, with particular rules relating to thein. 8. The doctrine of sophisms, or false reasoning, together with the means of avoiding them, and the snanner of solving or answering them. 4. Some general rules to direct our reasoning.
CHAP. I.--Of the Nature of a Syllogism, and the Parts of
which it is composed.
IF the mere perception and comparison of two ideas would always shew us whether they agree or disagree; then all rational propositions would be matters of intelligence, or first prio
ciples, and there would be no use of reasoning, or drawing any consequences. It is the narrowness of the human mind wbich introduces the necessity of reasoning. When we are unable to judge of the truth or falsehood of a proposition in an immediate mander, by the mere contemplation of its subject and predicate, we are then constrained to use a medium, and to compare each of them with some third idea, that by seeing how far they agree or disagree with it, we may be able to judge how far they agree or disagree among themselves : as, if there are two lines, A and B, and I know not whether they are equal or no, I take a third line C, or an inch, and apply it to each of them; if it agree with them both, then 1 infer that A and B are equal; but if it agree with one and not with the other, then I conclude A and B are unequal : if it agree with neither of them, there can be no comparison.
So, if the question be, whether God must be worshipped, we seek a third idea, suppose the idea of a Creator, and say,
Our Creator must be worshipped.
The comparison of this third idea, with the two distinct parts of the question, usually requires two propositions, which are called the premises : the third proposition which is drawn from them is the conclusion, wherein the question itself is answered, and the subject and predicate joined either in the negative or tbc affirmative.
The foundation of all affirmative conclusions is laid in this general truth, that so far as two proposed ideas agree to any third idea, they agree also among themselves. The character of Creator agrees to God, and worship agrees to a Creator, therefore worship agrees to God.
The foundation of all negative conclusions is this, that where one of the two proposed ideas agree with the third idea, and the other disagrees with it, they merst needs disagree so far also with one another; as, if no sinners are happy, and if angels are happy, then angels are not sinners.
Thus it appears what is the strict and just notion of a syllogismn : It is a sentence or argument made up of three propositions, so disposed, as that the last is necessarily inferred from those which go before, as in the instances wlrich have been just mentioned.
In the constitution of a syllogism two things may be considered, viz. the matter and the form of it.
The matter of wtricb a syllogism is made up, is three prox positions ; and these three propositions are made up of three ideas or terms variously joined. The three terms are called the remote matter of a syllogism; and the three propositions thin proxime or immediate matter of it. The three terms are named the major, the minor, and the middle. The predicate of the conclusion is called the major term, because it is generally of a larger exteosion than the minor term, or the subject. The major and minor terms are called the extremes. The middle terit is the third idea, iuvented and disposed in two propositions, ia such a manner as to shew the connection between the major animi minor term in the conclusion; for which reason the middle term itself is sometimes called the argument.
That proposition which contains the predicate of the conchision, connected with the middle term, is usually called the maji proposition, whereas the minor proposition connects the midi ir term with the subject of the conclusion, and is soinetimes called the assumption.
Note, This exact distinction of the several parts of a syllagism, and of the major and minor terms connected with tire miel dle term in the major and mixer propositions, dous chiefly belong to simple or categorical syllogisms, of which we shall speak in the next chapter, though all syllogisms whatsoever bave some-. thing analogical to it.
Note farther, That the major proposition is generally placed first, and the minor second, and the conclusion in the last place, where the syllogisın is regularly composed and represented.
The form of a syllogism is the framing and disposing of the premises according to art, or just principles of reasoning, and ilie regular inference of the conclusion from them.
The act of reasoning, or inferring one thing from another, is generally expressed and known by the particle therefore, when the argument is formed according to the rules of art; though in coinmon discourse or writing, such causal particles as for, because, manifest the act of reasoning as well as the illative particles then and therefore ; and wheresoever any of these words are used, there is a perfect syllogism expressed or implied, though perhaps the three propositions do not appear, or are not placed in regular form.
CHAP. II.-Of the various kinds of Syllogisms, with parti
cular Rules reluting to them. SYLLOGISMS are divided into various kinds, either according to the question which is proved by them, according to the nature and composition of them, or according to the middle term, which is used to prove the question. Sect. I.–Of unitersal and particular Syllogisms, both negatite
and affirmative. ACCORDING to the question which is to be proved, so syllogisms are divided into universal affirmative, universal negative, purricular affirmative, and particular negative. This is often called a division of syllogisms drawn from the conclusion; for so many sorts of conclusions there may be, which are marked with the letters A, E, I, O.
In an universal affirmative syllogism, one idea is proved universally to agree with another, and may be universally affirmed of it; as, every sin deserves death, every unlawful wish is a sin ; therefore every unlawful wish deserves death.
1 In an universal negative syllogism, one idea is proved to disagree with another idea universally, and may be ihus denied of it.; as, no injustice can be pleasing to God; all persecution for the sake of conscience is injustice; therefore no persecution for conscience sake can be pleasing to God.
Particular affirmative and particular negative syllogisms, may be easily understood by what is said of universals, and there will be sufficient examples given of all these in the next section.
The general principle upon which these universal and particular syllogisms is founded, is this, Whatsoever is affirmed or denied universally of any idea, may be affirmed or denied of all the particular kinds or beings, which are contained in the extension of that universal idea. So the desert of death is affirmed universally of sin, and an unlawful wish is one particular kind of sin, which is contained in the universal idea of sin, therefore the desert of death may be affirmed concerning an unlawful wisk. And so of ibe rest.
Note, In the doctrine of syllogisms, a singular and indefinite proposition are ranked among universals, as was before observed in the doctrine of propositions. Sect. II.-Of plain, simple Syllogisms, and their Rulcs.
THE next division of syllogisms is into single and compound. This is drawn from the nature and composition of them.
Single syllogisms are made up of three propositions, compound syllogisms contain more than three propositions, and may be formed into two or more syllogisms. Single syllogisms, for distinction's sake, may be divided icto *simple, complex, and conjunctive.
Those are properly called simple or categorical syllogisms, which are made up of three plain, single or categorical propositions, wherein the middle term is evidently and regularly joined with one part of the question in the major proposition, and with the other in the minor, whence tbere follows a plain single conclusion ; as “every human virtue is to be sought with diligence : prudence is a human virtue; therefore prudence is to be sought diligently."
Note, Though the terms of propositions may be complex ; yet where the composition of the whole argument is thus plain, simple, and regular, it is properly called a simple syllogism, since the complexion does not belong to the syllogistic form of it.
Simple syllogisms have several rules belonging to them, which being observed will generally secure us from false inferences ; but these rules being founded on four general axioms, it is necessary to mention these axioms beforehand, for the use of those who will enter into the speculative reason of all these rules :
I. Particular propositions are contained in universals, and
* As ideas and propositions are divided into single and compound, aod vingle are subdivided into siaple and complex; so there are the same divisions and subdivisious applied to syllogisme.