INDUCTIVE LOGIC.

CHAPTER I.

INTRODUCTORY.

INDUCTIVE Logic is the Science of the Discovery of Facts not directly observable. A few facts are known to us without discovery. Such are our personal idenobligation. A few truths

tity, moral freedom, and also are recognized by the mind as certain as soon as they are suggested. Evidence is not required to establish them, nor can it in any way confirm them. Of these are the axioms of Mathematics and the canons of Deductive Logic. This furniture is the same for all minds and the possession of it is what makes thinking possible. Only all minds do not with equal clearness analyze their own operations, and the most lack the patience, concentration, and strength to follow admitted principles to their ultimate consequences.

Whole sciences have been built up by simply developing the necessary implications of the few simple but universal truths intuitively perceived by every mind. Deductive Logic and Mathematics are examples. One peculiarity of them is that they are the same for all minds, and that when the terms used

are precisely understood there is no difference of opinion possible among sane men. These are pure sciences; they do not depend upon the actual existence of any person or thing, but we know that whatever does exist, necessarily conforms to them. If numbers or quantities of objects exist anywhere, they are in mathematical relations; if correct thinking upon any subject is done by rational beings anywhere, it is done according to the rules of deductive logic.

But the great bulk of our knowledge does not come to us by intuition. Beyond the few facts and truths with which the mind starts, lies the whole universe of reality, which we can know only through observation. Over against the pure sciences stand the applied sciences. The main value of the pure sciences is in the fact that they furnish the principles for constructing the applied sciences. The latter have no new formal principles of their own.

This last point is of supreme importance for the purpose now in hand. It has been extensively supposed that the field of thinking was divided into two kingdoms, ruled by two sovereigns, Deductive and Inductive Logic, under dissimilar constitutions, and that what was bad law in one kingdom might be good law in the other. It has been assumed that sometimes two thoughts which could show no right to union in the domain of Deduction could cross the border and, by a sort of Gretna Green marriage, make a synthesis in the kingdom of Induction. A little reflection should have shown all this to be a huge mistake. The canons of deductive logic are the universal laws of thought. They are invariably true, if ever true. The only

ground upon which we assent to any principle in deductive logic is our instant perception of its necessary and universal validity. If so, we cannot step into another province and escape its force. The limits of its domain are the same as those of correct thinking.

Deductive and Inductive Logic are not two sister sciences which divide the empire of thinking between them. They are not mutually exclusive; one does not stop where the other begins. One is not the inverse of the other. One does not proceed from generals to particulars, while the other moves from particulars to generals. It is not true that one infers from the known to the known, while the other infers from the known to the unknown. It is not true that one is rigorously required to draw conclusions no wider than its premises, while the other is warranted in concluding the universal from a part. Many such assertions have been made by philosophers, but it is obvious without discussion that, if there is any truth in deductive logic, all these assertions are false; for deductive logic sways a universal scepter or none. There can be no legitimate thinking except according to its laws. Inductive Logic is simply deductive logic regulating our reasoning upon our observations of the phenomena of the universe. It is deductive logic applied in the realm of reality. Whenever in our thinking a proposition is introduced the truth of which depends not upon its harmony with a previous admission, but directly upon observation, there our reasoning becomes Inductive. There is no new way of inferring peculiar to Induction. Deductive logic deals with the mutual harmony of propositions. Inductive logic deals with the harmony

between propositions and facts.

No reasoning of any

kind, deductive or inductive, can ever carry knowledge a step forward into the unknown, or do anything more than unfold what is contained in the premises.

We can learn the unknown only by observation; we can reason upon our observations in no other way than deductively; for that is the only way men can reason at all. The rational action of the mind upon the data of observation is called Induction.

In defining Inductive Logic as the science of the Discovery of Facts we use the word discovery in the strictest sense, as meaning the ascertainment of the absolutely unknown.

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To quote from Archbishop Whately :

"There certainly are two kinds of New Truth' and of Discovery,' if we take those words in the widest sense in which they are ever used. First, such truths as were, before they were discovered, absolutely unknown, being not implied in anything we previously knew, though we might perhaps suspect them as probable; such are all matters of fact strictly so-called, when first made known to one who had not any such previous knowledge as would enable him to ascertain them a priori, i.e., by reasoning; as, if we inform a man that we have a colony at Botany Bay; or that the earth is such a distance from the sun; or that platina is heavier than gold. The communication of this kind of knowledge is most usually and most strictly called information; we gain it from observation, and from testimony; no mere internal workings of our own minds (except when the mind itself is the very object to be observed), or mere discussions in words will make these known to us; though there is great room for sagacity in judging what testimony to admit, and forming conjectures that may lead to profitable observation, and to experi

ments with a view to it. The other class of Discoveries is of a very different nature. That which may be elicited by Reasoning,

and consequently is implied in that which we already know, we assent to on that ground, and not from observation or testimony: to take a geometrical truth upon trust, or to attempt to ascertain it by observation, would betray a total ignorance of the Science." 1

In the following treatise we shall first inquire what is meant by "a fact," and shall then follow as exactly as possible the processes of mind by which facts are ascertained. The several fallacies to which the unwary are exposed will receive a large share of attention. The points to be considered will require hard thinking, but if any advance in clearness is made, the labor will be well repaid; for inductive thinking is the largest part of the work of life.

1 Whately's Logic, p. 216.