LOGIC. 



OBJECTS OF LOGIC. 



HPHE objects of Logic, as of Grammar and 

 J. Rhetoric, are partly theoretical and partly 

 practical ; partly to give you general ideas con- 

 cerning the nature of names ; assertions, the foun- 

 dations of reasoned truth, and the various depart- 

 ments of thought and inquiry ; partly to warn you 

 against the fallacious tendencies of the human 

 mind, and to teach you the conditions that must 

 be observed in all departments of thought and 

 inquiry before you- can attain to true conclusions. 

 Men may reason correctly without knowing Logic, 

 as they may write correctly without knowing 

 Grammar, or convince an assembly without 

 knowing Rhetoric : these things are done every 

 day without a conscious knowledge of any rules 

 whatsoever ; but Logic teaches you the ultimate 

 nature of what you are reasoning about, of the 

 instrument that you employ, and of the grounds 

 whereon you rest when your reasonings are sound. 

 And this knowledge is both interesting and profit- 

 able. It may not guide you to great discoveries ; 

 it may not preserve you from all errors of reason- 

 ing ; it will not eradicate all the fallacious tenden- 

 cies of your mind, but it will help. 



The science of Logic has had two great starts 

 in history, both originating in practical necessities. 

 The first was given by Aristotle, the second by 

 John Stuart Mill. The Deductive Logic of Aris- 

 totle was suited to the wants of the Athenian 

 people in their Public Assembly and Courts of 

 Law. An audience met to hear a question argued 

 and to form an opinion, have to be guarded 

 against specious inferences from their accepted 

 beliefs ; it is good for them to know the correct 

 forms for the application of general principles to 

 particular cases, and the ways in which these forms 

 most readily become obscured so as to cheat them 

 into erroneous conclusions. This, in the main, was 

 the practical side of Aristotle's logic. In like man- 

 ner, the Inductive Logic of Mill was suited to the 

 interest in modern research. Mill did not invent 

 the canons of valid induction or the conditions of 

 valid hypothesis : these had been acted upon more 

 or less vaguely by reasoners in all times, and had 

 even been formulated by men of science ; but 

 Mill was the first to conceive the idea of including 

 them within the domain of Logic, and referring 

 them to the fundamental principles of reasoning. 

 Agreeably to their origin, the practical value of 

 Deductive Logic is to help in securing con- 

 sistency ; of Inductive, to help in securing truth.* 



NAMES, CLASSES, AND PROPOSITIONS. 



Both Deductive and Inductive Logic profess to 

 exhibit the ultimate grounds of Belief; and all 



* The present paper follows the arrangement and treatment of 

 the subject in Professor Bain's Logic, to which the reader is referred 

 for fuller information. 



75 



communications between men of matter for belief 

 or disbelief are made through the instrumentality 

 of language, and in the form of what we call in 

 common speech Assertions, in Grammar, Sen- 

 tences, and in Logic, Propositions. 



A matter of belief is something that we can act 

 upon ; something that will enable us to do one 

 thing for the sake of attaining some other thing. 

 When we say ' bread is nourishing,' we do more 

 than announce an object, ' bread,' and a property, 

 ' nourishing : ' we tie these two things together 

 with a bond of union which rouses the activity of 

 the human mind, and causes it to set to work in 

 some given course. Belief is the state preliminary 

 to action, or the state disposing to action when 

 some given emergency arises ; and assertions or 

 propositions are the subject-matter of this faith or 

 belief. 



An assertion requires, in the first place, that 

 there should be two things mentioned ; it is not 

 possible so to mention a single object as that 

 it shall be a matter of belief or disbelief. Thus, 

 ' fire burns,' ' gold is yellow,' ' bread is nourishing,' 

 ' the sun is the centre of the planetary motions ' 

 each contains at least two things or notions 

 coupled together. Fire is one thing, burning is a 

 different thing, if there be any meaning or any- 

 thing to believe in the assertion. But the mention 

 of two things is not enough ; the two names of 

 ' gold,' ' yellow colour,' do not make an assertion 

 of themselves ; the asserting power is conferred 

 by the verb 'is;' and we shall find that every 

 assertion requires a verb, or that the verb is the 

 part of speech which completes the force of an 

 assertion, or has the power of causing belief or 

 disbelief in the human mind. 



As an assertion, therefore, requires the mention 

 of two things, ' every proposition must contain two 

 terms. Of these two terms, the one that is spoken 

 of is called the subject ; what is said of it, the 

 predicate; and these two are called the terms (or 

 extremes), because, logically, the Subject is placed 

 first, and the Predicate last; and in the middle 

 the copttla, which indicates the act of judgment, as 

 by it the Predicate is affirmed or denied of the 

 Subject.' Whately. Thus, in the above instance, 

 'gold,' the thing spoken of, is the subject; 'yellow,' 

 the predicate ; and ' is,' the copula. The verb 'to 

 be ' is the most universal copula, and every other 

 mode of affirmation or denial might be reduced to 

 it. 



The Different Kinds of Names. 



The terms of a proposition, its subject and its 

 predicate, must be names ; hence, every propo- 

 sition must contain at least two names, and it 

 becomes necessary for the logician to consider the 

 nature of names so far as that may affect logic. 

 Other sciences and arts that have to deal with 

 names Philology, Grammar, Rhetoric divide 

 names into classes, to suit their particular pur- 

 posesAryan and Semitic ; nouns, adjectives, 

 verbs ; plain and figurative, stirring and pathetic : 



