BOOK IV.

DISSERTATION ON THE PROVINCE OF REASONING.

LOGIC being concerned with the theory of Reasoning, it is evidently necessary, in order to take a correct view of this Science, that all misapprehensions should be removed relative to the occasions on which the Reasoning-process is employed, the purposes it has in view, and the limits within which it is confined.

Simple and obvious as such questions may appear to those who have not thought much on the subject, they will appear on further consideration to be involved in much perplexity and obscurity, from the vague and inaccurate language of many popular writers. To the confused and incorrect notions that prevail respecting the Reasoning-process may be traced most of the common mistakes respecting the Science of Logic, and much of the unsound and unphilosophical argumentation which is so often to be met with in the works of ingenious writers.

These errors have been incidentally adverted to in the foregoing part of this work; but it may be desirable, before we dismiss the subject, to offer on these points some further remarks, which could not have been there introduced without too great an interruption to the development of the system. Little or nothing indeed remains to be said that is not implied in the principles which have been already laid down; but the results and applications of those principles are liable in many instances to be overlooked, if not distinctly pointed out. These supplementary observations will neither require, nor admit of, so systematic an arrangement as has hitherto been aimed at; since they will be such as are suggested principally by the objections and mistakes of those who have misunderstood, partially or entirely, the nature of the Logical system.

Let it be observed, however, that as I am not writing a review or commentary on any logical works, but an introduction to the science, I shall not deem it necessary to point out in all cases the agreement or disagreement between other writers and myself, in respect of the views maintained, or the terms employed, by each.

CHAP. I.-Of Induction.

§ 1.

opposing

MUCH has been said by some writers of the superiority of the Mistake of Inductive to the Syllogistic method of seeking truth; as if the two Induction to stood opposed to each other; and of the advantage of substituting Syllogism. the Organon of Bacon for that of Aristotle, &c. which indicates a total misconception of the nature of both. There is, however, the more excuse for the confusion of thought which prevails on this subject, because eminent Logical writers have treated, or at least have appeared to treat, of Induction as a kind of Argument distinct from the Syllogism; which if it were, it certainly might be contrasted with the Syllogism: or rather, the whole Syllogistic theory would fall to the ground, since one of the very first principles it establishes, is that all Reasoning, on whatever subject, is one and the same process, which may be clearly exhibited in the form of Syllogisms. It is hardly to be supposed, therefore, that this was the deliberate meaning of those writers; though it must be admitted that they have countenanced the error in question, by their inaccurate expressions.

of the word

This inaccuracy seems chiefly to have arisen from a vagueness in Two senses the use of the word Induction; which is sometimes employed to Induction. designate the process of investigation and of collecting facts; sometimes, the deducing of an inference from those facts. The former of these processes (viz. that of observation and experiment) is undoubtedly distinct from that which takes place in the Syllogism; but then it is not a process of argumentation; the latter again is an argumentative process; but then it is, like all other arguments, capable of being Syllogistically expressed. And hence Induction has come to be regarded as a distinct kind of argument from the Syllogism. This Fallacy cannot be more concisely or clearly stated, than in the technical form with which we may now presume our readers to be familiar.

“Induction is distinct from Syllogism:

Induction is a process of Reasoning;" therefore

"There is a process of Reasoning distinct from Syllogism." Here" Induction," which is the Middle-Term, is used in different senses in the two Premises.

Induction, so far forth as it is an argument, may, of course, be stated Syllogistically: but so far forth as it is a process of inquiry with a view to obtain the Premises of that argument, it is, of course, out of the province of Logic: and the latter is the original and strict sense of the word. Induction means properly, not the inferring of the conclusion, but the bringing in, one by one, of instances,

of Induction

bearing on the point in question, till a sufficient number has been collected. The ambiguity, therefore, above alluded to, and which has led to much confusion, would be best avoided by saying that Proper sense we do not, strictly speaking, reason by Induction, but reason from Induction: i.e. from our observations on one, or on several Individuals, (ix rãv xal Exaσtov) we draw a Conclusion respecting the Class ( xάbonov) they come under: or, in like manner, from several Species, to the Genus which comprehends them:—in logical language, what we have predicated of certain singular-terms, we proceed to predicate of a common-term which comprehends them; -or proceed in the same manner from Species to Genus. E.G. "The Earth moves round the Sun in an elliptical orbit; so does Mercury; and Venus; and Mars, &c.: therefore a Planet (the common-term comprehending these singulars) moves round," &c. Philip was reckless of human life; so was Alexander; and J. Cæsar; and Augustus, &c.: therefore this is the general character of a Conqueror."

Inductive
Argument
expressed in
Syllogism,

figure.

66

Now it appears as if the most obvious and simplest way of filling up such enthymemes as these, expressed as they are, would be, in the third figure; having of course a particular Conclusion:

"Earth, Mercury, Venus, &c. move, &c. Mi. These are planets; therefore

Some planets move, &c."

But when we argue from Induction we generally mean to infer more than a particular conclusion; and accordingly most logical writers present to us the argument in the form of a syllogism in Barbara; inserting, of course, a different minor premiss from the foregoing, in the first viz. the simple converse of it. And if I am allowed to assume, not merely that "Mercury, Venus, and whatever others I may have named, are Planets," but also, that "All Planets are these "that these are the whole of the individuals comprehended under the Term Planet-I am, no doubt, authorized to draw a universal conclusion. But such an assumption would, in a very great majority of cases where Induction is employed, amount to a palpable falsehood, if understood literally. For it is but seldom that we find an instance of what Logicians call a "perfect-induction;" viz. where there is a complete enumeration of all the individuals, respecting which we assert collectively what we had before asserted separately; as "John is in England; and so is Thomas; and so is William; and all the sons of such-a-one are John, Thomas, and William; therefore all his sons are in England." Such cases, I say, seldom occur; and still more rarely can such an Induction (which Bacon characterizes res puerilis "1)—-since it does not lead the mind from what

Perfect-
Induction.

as

66

1 It may very well happen too, that (as in the example above) a certain circumstance may, in fact, belong to each individual of a certain class, and yet may have

no connexion, except accidentally, with the Class itself, as such; i.e. with the description of it, and that which constitutes it a Class. (See Appen. II. Ex. 118.

is better-known to what is less-known-serve any important purpose.

But in such Inductions as are commonly employed, the assumption of such a minor-premiss as in the above example, would be, as I have said, strictly speaking, a false assumption. And accordingly those logicians who state an argument from Induction in the above form, mean, I apprehend, that it is to be understood with a certain latitude; i.e. that, in such propositions as "all planets are Mercury, Venus, &c.," or "all Conquerors are Philip, Alexander, and Cæsar," they mean (by a kind of logical fiction) to denote that "all Conquerors are adequately represented by Philip, Alexander, &c."-that these individual persons or cases are a sufficient sample, in respect of the matter in question, of the Class they belong to.

premiss

I think it clearer, therefore, to state simply and precisely what it The Major is that we do mean to assert. And in doing this, we shall find that suppressed. the expressed premiss of the enthymeme, viz.: that which contains the statement respecting the individuals—is the Minor; and that it is the Major that is suppressed, as being in all cases substantially the same: viz. that what belongs to the individual or individuals we have examined, belongs (certainly, or probably, as the case may be) to the whole class under which they come. E.G. From finding on examination of several sheep, that they each ruminate, we conclude that the same is the case with the whole Species of sheep: and from finding on examination of the sheep, ox, deer, and other animals deficient in upper cutting-teeth, that they each ruminate, we conclude (with more or less certainty) that quadrupeds thus deficient are ruminants: the hearer readily supplying, in sense, the suppressed major premiss; viz. that "what belongs to the individual sheep we have examined, is likely to belong to the whole species;" &c.

Whether that which is properly called Induction (viz. the inquiry respecting the several individuals or species) be sufficiently ample, i.e. takes in a sufficient number of individual, or of specific cases,whether the character of those cases has been correctly ascertained -and how far the individuals we have examined are likely to resemble, in this or that circumstance, the rest of the class, &c. &c., are points that require indeed great judgment and caution; but this judgment and caution are not to be aided by Logic; because they are, in reality, employed in deciding whether or not it is fair and allowable to lay down your Premises; i.e. whether you are authorized or not, to assert, that "what is true of the individuals you have examined, is true of the whole class:" and that this or that is true of those individuals. Now, the rules of Logic have nothing to do with the truth or falsity of the Premises; except, of course, when they are the conclusions of former arguments; but merely teach us to decide, not, whether the Premises are fairly laid down, but whether the Conclusion follows fairly from the Premises or

not.

assuming & Premiss.

Necessity of It has however been urged that what are described as the MajorMajor- premises in drawing inferences from Inductions, are resolvable ultimately into an assertion of the "Uniformity of the laws of Nature,' or some equivalent proposition; and that this is, itself, obtained by Induction; whence it is concluded that there must be at least one Induction-and that, the one on which all others depend-incapable of being exhibited in a Syllogistic form.

A зsumption of Premises

in

Induction.

But it is evident, and is universally admitted, that in every case where an inference is drawn from Induction (unless that name is to be given to a mere random guess without any grounds at all) we must form a judgment that the instance or instances adduced are "sufficient to authorize the Conclusion ;"-that it is "allowable" to take these instances as a sample warranting an inference respecting the whole Class. Now the expression of this judgment in words, is the very Major-premiss alluded to. To acknowledge this, therefore, is to acknowledge that all reasoning from Induction without exception does admit of being exhibited in a syllogistic form; and consequently that to speak of one Induction that does not admit of it, is a contradiction.

Whether the belief in the constancy of Nature's laws,- -a belief of which no one can divest himself—be intuitive and a part of the constitution of the human mind, as some eminent metaphysicians hold, or acquired, and in what way acquired, is a question foreign to our present purpose. For that, it is sufficient to have pointed out that the necessity of assuming a universal Major-premiss, expressed or understood, in order to draw any legitimate inference from Induction, is virtually acknowledged even by those who endeavour to dispute it.

§ 2.

Whether then the Premiss may fairly be assumed, or not, is a point which cannot be decided without a competent knowledge of the nature of the subject. E.G. In most branches of Natural-philosophy, in which the circumstances that in any case affect the result, are usually far more clearly ascertained than in human affairs, a single instance is usually accounted a sufficient Induction; e.g. having once ascertained that an individual magnet will attract iron, we are authorized to conclude that this property is universal. Meteorology, however, and some other branches of Natural-philosophy, in which less advancement has been made, a much more copious Induction would be required. And in respect of the affairs of human life, an inference from a single instance would hardly ever be deemed allowable.

In

But it is worth remarking, that in all cases alike, of reasoning from Induction, the greater or less degree of confidence we feel is always proportioned to the belief of our having more or less completely ascertained all the circumstances that bear upon the question.