rogatories, afforded by experimental results, acknowledge the only real testimony to physical truth; the only means by which the laws of the material world can be successfully elicited and established; and by which simplicity and order are educed out of the vast mass and (as might appear) inextricable complexity of accumulated phenomena.

The claims of the Inductive Philosophy are indeed now generally allowed, and its praises held forth; still, not unfrequently, even its advocates and encomiasts entertain very indistinct notions of the real nature of the system they support, and it becomes the more necessary to examine carefully the nature of the reasoning, and the general grounds of the evidence, by which experimental laws, and physical truths, are substantiated; and this, in fact, is what is meant by the expressions so commonly used, "the inductive method," "the inductive logic," experimental evidence," and the like. The object of the present section is to analyze their meaning, and endeavour to exemplify and elucidate the nature of our convictions and inferences, in these branches of knowledge; the degree of certainty of which they are susceptible; and the sources of failure and error to which we are most exposed in the prosecution of physical inquiry, without some well-grounded principles of this kind as our guide. And without restricting ourselves to too formal and technical a method, to examine briefly the real nature of the inductive process: and to illustrate, by familiar examples, wherein the most essential and characteristic

features of inductive evidence consist, as distinguished on the one hand from the mere evidence of our senses, and on the other from demonstration.

Meaning and Nature of Induction.

AT the present day, so common is the use of the term "Inductive Philosophy," that, it may be presumed, there are few persons who have not at least some apprehension of the sort of investigation which it is used to designate.

In its more general signification, this term is employed to describe the entire method of modern physical science, as peculiarly characterized by resting on the appeal to experiment and observation alone; and as contra-distinguished from the scholastic systems, which proposed to reason downwards from abstract principles to natural laws and phenomena: the inductive, on the contrary, ascends from observed phenomena to general laws and abstract principles.

In its more limited sense, however, " induction" is understood to signify the process of inferring and collecting general results, general facts, or "laws," from a number of particular instances, carefully established on actual experimental evidence. It is the nature of the process, thus designated, and the principles on which it is conducted, that we propose to explain and comment upon.

Now, it is clear that the first step in such a process, must be the collection and classification of a number of particular phenomena: the careful exa

mination of a number of individual cases, in order to discover some common property or circumstance in which they all agree, amid many others in which they differ*.

Does then the process consist merely in this, that we examine every individual of a class, or number of objects before us, and, finding each one to possess a particular property, affirm that as a common property of the class? This, certainly, would imply no exercise of reasoning, and would hardly be worthy the name of induction. We should be merely affirming a proposition for whose truth we had the direct evidence of our senses. Yet perhaps among cases even of this sort, there may exist much difference as to the extent and labour of the research we may have to go through, in detecting the one property, which is common to all the individual cases, and constitutes the characteristic by which we give them a common classification and a generic name. The point in which all the examined instances agree, may, indeed, be manifest at first sight. But, again, it may be far otherwise; and though we have all the cases before us, (especially if they be numerous,) it may yet require no small labour and skill to succeed in tracing out what the property or circumstance is in which they all agree, amidst a variety of others in which they differ. The first case requires nothing further than the bare inspection of the instances.

* This "bringing in," as it were, of fresh testimony, and corroborating witnesses, was probably the original idea of “inductio," or ἐπαγωγή.

The latter may call forth much discriminative skill. The former is the work of the mere collector: the latter may involve that of the philosopher. But in any case other than the most immediately obvious, there is this to be remarked; and it is deserving of particular attention: it is almost certain that, in the first instance, the mind will conjecturally fix upon some property, which is imagined (whether correctly or not) most likely to be the common one sought, long before a complete examination of all the individuals has taken place*.

Let us suppose, on the other hand, that we have not all the individual facts before us. We observe a certain number of them, and finding them agree in some property, we are almost invariably prone at once to infer, that all the rest possess it likewise. We infer more than we see. There is certainly a strong natural tendency in the human mind (even upon very slight apparent grounds) to advance from individual facts to general conclusions, to hazard inferences from the known to the unknown.

Grounds of Inductive Conclusion.

We have then next to inquire with what reasonable confidence can we make such inference? For instance, suppose that feeling a number of balls in a bag, we take out a few, and, finding them white, infer that all the balls in the bag are white: is this a legitimate induction? Is it correct reasoning; is

* See Sir John Herschel's Introductory Discourse on Natural Philosophy, p. 165.

it not rather a most groundless presumption? Yet it may be asked, does it not possess all the characteristics of induction, as they have been laid down by some logical writers? For wherein does the case we have supposed, differ from their commonly cited example: " This, that, and the other loadstone, attracts iron,-therefore all loadstones do?" Or why is not the former of these instances as good reasoning as the latter?

In the case of the balls, we cannot assign or imagine any reason why one should be white because others are so; any supposable connexion between the circumstance of the balls being together in the bag, and their colour. There is no tendency to fancy or expect it. On the other hand, in the case of the loadstone, having observed the effect, in a few instances, we feel a natural tendency to imagine that the same magnetic property subsists whenever we perceive the same external characteristics. We cannot avoid being persuaded that there is a connexion between that particular darkness of colour, weight, hardness, texture, &c., by which we recognise the mineral, and a magnetic power, though we may be at a loss to explain or assign the ground for it.

Yet the only thing which seems at all to warrant the induction from a limited number of instances, is the reasonableness of such an intuitive persuasion. When, therefore, we have only a limited number of instances, which we can examine (and such is the

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