DR. REID'S ANALYSIS. 201 the predicate of the minor premise. The following is a particular example of the second figure: Socrates was an ugly man; Plato was not an ugly man; Therefore, Plato was not Socrates. The middle term, "ugly," is the predicate of both premises. The same logician supplies a particular example of the third figure: Judas did not obtain salvation; Judas was an apostle; Therefore, every apostle did not obtain salvation. 66 Judas," is the middle term, and the subject of both premises, according to the requisitions of the third figure.* [* Dr. Thomas Reid presents the following analysis of the three syllogistic figures explained in the preceding lecture. He remarks: The compass of the syllogistic system as an engine of science, may be discerned by a compendious and general view of the conclusion drawn, and the argument used to prove it, in each of the three figures. In the first figure, the conclusion affirms or denies something of a certain species or individual; and the argument to prove this conclusion is, that the same thing may be affirmed or denied of the whole genus to which that species or individual belongs. In the second figure, the conclusion is, that some species or individual does not belong to such a genus; and the argument is, that some attribute common to the whole genus does not belong to that species or individual. In the third figure, the conclusion is, that such an attribute belongs to part of a genus; and the argument is, that the attribute in question belongs to a species or individual which is part of that genus. I apprehend that, in this short view, every conclusion that falls within the compass of the three figures, as well as the means of proof, is comprehended. The rules of all the figures might be easily deduced from it; and it appears that there is only one principle of reasoning in all the three; so that it is not strange that a syllogism of one figure should be reduced to one of another figure. The general principle in which the whole terminates, and of which every categorical syllogism is only a particular application, is this, that what is affirmed or denied of the whole genus, may be affirmed or denied of every species and individual belonging to it. This is a principle of undoubted certainty indeed, but of no great depth. Aristotle and all the logicians assume it as an axiom or first principle from which the syllogistic system takes its departure; and after a tedious voyage, and great expense of demonstrations, it lands at last in this principle as its ultimate conclusion. O curas hominum! O quantum est in rebus inane !-Reid's Works, vol. i. p. 108.] SYLLOGISM-ITS MERIT AS A MODE OF REASONING. BESIDES regular, categorical, or pure syllogisms, there are others called irregular, because they cannot be reduced to the rules of mode and figure. I shall briefly explain the nature of these, more in conformity with general practice, than because they are of much importance. * Enthymeme is the first species I shall mention. It takes place when one of the propositions which constitute the premises is omitted, and the conclusion is drawn from the other premise, as if the syllogism were regular and complete. The following is an example. If I say, either, Or, Whatever thinks is a spiritual substance, Therefore, the mind of man is a spiritual substance; The mind thinks, Therefore, the mind is a spiritual substance; I omit the minor proposition in the former case, and infer the conclusion from the major. I omit the major proposition in the latter case, and infer the same conclusion from the minor. It is supposed in both cases that the connection of the conclusion with either premise, is so apparent as to render unnecessary the pres [* Gr. ev, and Ovμos, mind; something understood in the mind, and not expressed.-Brande. "What is an enthymeme?" quoth Cornelius. "Why, an enthymeme," replied Crambe, "is when the major is indeed married to the ininor, but the marriage kept secret."-Arbuthnot and Pope.] ence of the other premise. The premise in this case is called the antecedent; and the conclusion, the sequela, or the inference.* Sorites is another species of irregular syllogism, and consists in conjoining a series of propositions in such a manner, that the predicate of the preceding proposition forms the subject of the succeeding. The following is an example: The mind is a thinking substance. A thinking substance is a spirit. A spirit has no extension. What has no extension has no parts. What has no parts is indissoluble. What is indissoluble is immortal. Therefore, the mind is immortal. This species, like the former, is only a train of syllogisms abridged, into which it may easily be resolved in the following manner: All thinking substances are spirits ; Spirits have no extension; The mind is a spirit; Therefore, it has no extension. Things having no extension have no parts; Therefore, it has no parts. [* The arguments used in thinking, speaking, or writing, are never drawn out in strict technical form, except by practised logicians, desirous of exhibiting their art to those who, like themselves, are conversant with it. A sentence which contains the materials of a syllogism, not technically expressed, has been called an enthymeme. Aristotle understands by this a syllogism such as would be used in rhetoric, where the full and orderly expression of premises and conclusion would seem labored and artificial. And as the omission of one of the premises is a common, perhaps the commonest, feature of enthymemes, logicians have defined them as syllogisms with one premise suppressed. But we may also omit the conclusion, or invert the order of premises and conclusion; and unless we extend the name enthymeme to these cases, we put a considerable restriction upon its original meaning. Let the enthymeme then be defined-an argument in the form in which it would naturally occur in thought or speech.-W. Thomson.] 204 CONDITIONAL SYLLOGISM. Things having no parts are indissoluble; Therefore, the mind is indissoluble. Things indissoluble are immortal; Therefore, the mind is immortal. Hence it appears, that all the intermediate propositions between the first and the last of a Sorites may be formed into separate syllogisms; and that it is equivalent to an argument formed of as many syllogisms as the argument contains intermediate propositions. It may also be observed, that every idea of the Sorites is twice repeated, and that it might be further abridged without any detriment to the evidence it communicates. Had it stood as follows, the agreement of its ideas would have been as clear, and its evidence as satisfactory, as in any other form. Mind-thinking substance -spirit-without extension-without parts-indissoluble-immortal.* Irregular syllogisms, further, are either conditional or disjunctive. The subsequent is a conditional syllogism. "If the air press down bodies below it, it must be a heavy body." The legitimacy of this species of reasoning consists in the inference following necessarily from the premise. It has scarcely any logical form. It is an [* Three or more premises in which the predicate of each is the subject of the next, with a conclusion formed from the first subject and last predicate of the premises, have been called a sorites, or accumulating argument, from the Greek word owpòs, a heap. The name is not very appropriate; the German title of chain-argument (kettenschluss) expresses better the nature of the process in which the mind goes on from link to link in its reasoning, without thinking it necessary to draw out the conclusions as it passes. Where the premises are all universal affirmative judgments, not the least confusion can arise from thus postponing till the end the realization of the results. But where the premises are judgments of different kinds, the reasoning is more difficult to follow, and it may be necessary to draw out each syllogism separately, in order to see whether it is in a valid mood, and, if otherwise, what is the fault in it.-Thomson.] DISJUNCTIVE SYLLOGISM-DILEMMA. 205 inference from a principle, which inference must be admitted if the principle be granted. A disjunctive syllogism is proper and legitimate, when the predicate of the premise admits an alternative, and when the predicate and alternative involve every possible case. If the predicate be obviously false, the alternative of course must be true. Example: The mind of man is either corporeal or spiritual; If the predicate and the alternative do not exhaust every case that can exist, the conclusion will be illegitimate. For example: "All neighbors are either friends or enemies; they are not friends; therefore, they are enemies." In this instance, the predicate and the alternative do not include every case. The greatest part of neighbors may be neither friends nor enemies; they may be altogether indifferent, and accordingly the conclusion is ridiculous. [The Dilemma is a complex argument, partaking both of the conditional and disjunctive. It is a syllogism with a conditional premise, in which either the antecedent or consequent is disjunctive. It may prove a negative or an affirmative conclusion. The word Dilemma means "double proposition," so that the whole argument takes its name from the one mixed judgment in it. When this is more than double, as in, "If a prisoner is legally discharged, either the magistrate must refuse to commit, or the grand jury ignore the bill, or the common jury acquit, or the crown exercise the prerogative of pardon," the argument has been called a Trilemma, Tetralemma, or Polylemma, according to the number of members the judgment may have.--Thomson.] I observed, in the last lecture, that of the hundred |