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. 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 experiments 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. CHAPTER II. FACTS. SINCE Inductive Logic is the science of the Discovery of Facts, it is necessary to consider at the outset what is meant by a fact. The human mind finds itself in a universe of phenomena. Through the senses it has perceptions of an external world, and through consciousness it knows its own modifications. Through these channels alone can the mind advance in knowledge of realities. Whatever has real existence is a fact. It may be a substance, an energy, a quality, an action, a state, or only some relation of substances, energies, qualities, actions, or states, but if it be perceived by the mind it is a fact. A dragon is not a fact, because it is not perceived; but the notion of a dragon is a fact, for that is an action of the mind of which I am conscious. The sun is a fact, the continent of America is a fact; the yellow color of gold, the attraction of a magnet, the likeness of two peas, are facts. For the purposes of induction, facts may be classified as substantive facts and facts of relation. A substantive fact is a phenomenon considered apart, as independently existing. The yellowness of gold, the weight of gold, the malleability of gold, are substantive facts. A fact of relation connects in some way two substantive facts. That malleability and yellowness coexist in gold is a fact of relation. Facts of relation are of three kinds: Facts of Resemblance, Facts of Coexistence, and Facts of Causation. Facts of Succession are often named among the ultimate kinds, but, as we shall see later, they are dependent upon simpler facts of causation. One of the first lessons received by a child when it begins, as we say, to notice, is that there are many things in the world which resemble one another. Often the resemblance is so complete that the several phenomena seem but repetitions of the same thing. Thus from the observation of individual facts we pass through the perception of resemblances to the formation of a general concept. Common nouns are but the names of indefinite numbers of facts that resemble one another. The possibility of language arises from the constant repetition of similar things for which the same words will do. It is also observed that there are certain more or less constant groups of substantive facts. We repeatedly find yellowness, sweetness, roundness, etc., coexisting; and to this assemblage of phenomena we give the name orange. We find yellowness, malleability, specific gravity 19.32, etc., coexisting, and we call this group of coexistences gold. It is observed that when certain substantive facts or groups of substantive facts are in a certain collocation, a reaction occurs between them and that this is often attended by a change in one or more of the facts or groups. The relation between facts or groups of facts and their reactions, as well as the relation between any fact or group of facts and itself in a new form, is called Causation. |