Imágenes de páginas


most prevailing notion. Nor is this much to be wondered at; since it is evident to all, that some men converse and write, in an argumentative way, very justly on one subject, and very erroneously on another, in which again others excel, who fail in the former. This error may Reasoning be at once illustrated and removed, by consi- ar in all subdering the parallel instance of Arithmetic; in which every one is aware that the process of a calculation is not affected by the nature of the objects whose numbers are before us: but that

(e.g.) the multiplication of a number is the ✓ very same operation, whether it be a number of

men, of miles, or of pounds; though nevertheless persons may perhaps be found who are accurate in calculations relative to natural philosophy, and incorrect in those of politicaleconomy, from their different degrees of skill in the subjects of these two sciences; not surely because there are different arts of Arithmetic applicable to each of these respectively.

Others again, who are aware that the simple system of Logic may be applied to all subjects whatever, are yet disposed to view it as a peculiar method of reasoning, and not, as it is, a method of unfolding and analyzing our reasoning: whence many have been led (e. g. the author of the Philosophy of Rhetoric) to talk

! of comparing Syllogistic reasoning with Moral reasoning; taking it for granted that it is

possible to reason correctly without reasoning logically; which is, in fact, as great a blunder as if any one were to mistake grammar for a peculiar language, and to suppose it possible to speak correctly without speaking grammatically. They have in short considered Logic as an art of reasoning; whereas (so far as it is an art) it is the art of reasoning ; the logician's object being, not to lay down principles by which one may reason, but, by which all must reason, even though they are not distinctly aware of them: -to lay down rules, not which may be followed with advantage, but which cannot possibly be departed from in sound reasoning. These misapprehensions and objections being such as lie on the very threshold of the subject, it would have been hardly possible, without noticing them, to convey any just notion of the nature and design of the logical system.

§ 2. Supposing it then to have been perceived that the operation of reasoning is in all cases the same, the analysis of that operation could not fail to strike the mind as an interesting matter of inquiry. And moreover, since (apparent) arguments which are unsound and inconclusive, are so often employed, either from error or design; and since even those who are not misled by these fallacies, are so often at a loss

to detect and expose them in a manner satisfactory to others, or even to themselves; it could not but appear desirable to lay down some general rules of reasoning, applicable to all cases; by which a person might be enabled the more readily and clearly to state the grounds of his own conviction, or of his objection to the arguments of an opponent; instead of arguing at random, without any fixed and acknowledged principles to guide his procedure. Such rules would be analogous to those of Arithmetic, which obviate the tediousness and uncertainty of calculations in the head; wherein, after much labour, different persons might arrive at different results, without any of them being able distinctly to point out the error of the rest. A system of such rules, it is obvious, must, instead of deserving to be called the art of wrangling, be more justly characterised as the “ art of cutting short wrangling,” by bringing the parties to issue at once, if not to agreement; and thus saving a waste of ingenuity.

In pursuing the supposed investigation, it Analysis of will be found that every conclusion is deduced, in reality, from two other propositions; (thence called Premises;) for though one of these may be, and commonly is, suppressed, it must never- r theless be understood as admitted; as may easily be made evident by supposing the denial of the suppressed premiss, which will at once.


invalidate the argument: e.g. if any one, from perceiving that “the world exhibits marks of design,” infers that "it must have had an intelligent author," though he may not be aware in his own mind of the existence of any other premiss, he will readily understand, if it be denied that “whatever exhibits marks of design must have had an intelligent author,” that the affirmative of that proposition is necessary to the validity of the argument. An argument thus stated regularly and at full length, is called a Syllogism; which therefore is evidently not a peculiar kind of argument, but only a peculiar form of expression, in which every argument may be stated.

When one of the premises is suppressed (which for brevity's sake it usually is) the argument is called an Enthymeme. And it may be worth while to remark, that when the argument is in this state, the objections of an opponent are (or rather appear to be) of two kinds; viz. either objections to the assertion itself, or objections to its force as an argument. E.G. In the above instance, an atheist may be conceived either denying that the world does exhibit marks of design, or denying that it follows from thence that it had an intelligent author. Now it is important to keep in mind that the only difference in the two cases is, that in the one the expressed premiss is denied, in the

[ocr errors]

other the suppressed; forthe force as an argument of either premiss depends on the other premiss: if both be admitted, the conclusion legitimately connected with them cannot be denied.

It is evidently immaterial to the argument whether the conclusion be placed first or last; but it may be proper to remark, that a premiss placed after its conclusion is called the Reason* of it, and is introduced by one of those conjunctions which are called causal; viz. “since,” “because,” &c. which may indeed be employed to designate a premiss, whether it came first or last. The illative conjunctions, “therefore,” &c. designate the conclusion.

It is a circumstance which often occasions error and perplexity, that both these classes of conjunctions have also another signification,

being employed to denote, respectively, Cause ✓ and Effect, as well as Premiss and Conclusion:

e. g. If I say, “this ground is rich, because the trees on it are flourishing,” or “ the trees are flourishing, and therefore the soil must be rich," I employ these conjunctions to denote the connexion of Premiss and Conclusion; for it is plain that the luxuriance of the trees is not the cause of the soil's fertility, but only the cause of my knowing it. If again I say, “the trees flourish, because the ground is rich,"

* The Major-premiss is often called the Principle; and the word Reason is then confined to the Minor.

« AnteriorContinuar »