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EVIDENCE OF PHYSICAL TRUTH.
THE INDUCTIVE METHOD.
“ There is a certain analogy, constancy, and uniformity, in the phenomena or appearances of nature, which are a foundation for general rules; and these are a grammar for the understanding of nature, or that series of effects in the visible world, whereby we are enabled to foresee what will come to pass in the natural course of things.'
Bishop BERKELY, (Siris, p. 120.) “ Usque adeo natura, una eadem semper atque multiplex, disparibus etiam formis, effectus pares, admirabili quadam varietatum simplicitate, conciliat.”
The Inductive Philosophy stands forth as the distinguishing boast of modern intellectual advancement, and the prolific source of innumerable advantages,—mental, moral, and physical. It has opened the path now universally recognised as alone leading to the correct interpretation of nature; of that stupendous order of varied existence, and incessant activity of causation, with which we are surrounded and filled. It is justly characterized as a method framed in conformity to experience; and stands essentially opposed to those artificial systems of former ages, which were but the vain chimeras of minds bewildered in the obscurities of verbal mysticism, or deluded by the conceits of gratuitous hypothesis ; systems which cramped all energy of thought and invention, and fettered all freedom of opinion and discussion. By a combination of vague and unmeaning abstractions, involved in a pedantic jargon of empty terms, the scholastic disputants thought to settle the order of natural causes, and determine what must be the character of physical laws. From a few abstract, and those hardly intelligible, arbitrary positions, they affected to advance, by the mere subtilty of their reasoning powers, to a comprehension of the entire system of the material universe.
But the appeal to experiment and observation, and the high and pure physical philosophy inculcated by Bacon, and practically followed up by Galileo, Newton, and their successors, soon established the dominion of principles, at once more correct and rational, and better suited to the limited range of the human faculties. By the humble unpretending path of the inductive method, all the great triumphs of physical discovery have been achieved; by a steady adherence to its principles, can we alone expect the further extension of natural knowledge; and so long as they are adhered to, we can assign no limit to the progressive advance which may be made. And minds duly impressed with the sublimity of those inquiries which the contemplation of the universe suggests, will easily recognise the truth and value of this method. They perceive, in the reference to observation and experience, an appeal to the sole authority of nature: they would interrogate her in her own language, and in the replies to those inter
rogatories, afforded by experimental results, acknow, ledge 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