CAUSALITY or CAUSATION signifies the relation of cause and effect. Common sense assumes that things and events are the products or results of certain other things or events—the result is called the effect, and that which produces it is called the cause. The attempt to understand things usually takes the form of trying to discover their causes and effects. The belief in causes and effects is most probably derived partly from the human experience of exercising various activities in order to produce certain results or to achieve certain ends, and partly from the experience of suf fering the effects of the actions of others. In the early stages of human thought natural phenomena were (and in the case of the young or the undeveloped still are) conceived after the analogy of such human experiences of doing things and of being acted on, of causing effects or suffering them. The mythological accounts of natural phenomena abundantly illustrate the anthropomorphic tendencies in the early attempts to explain or to understand reality. With the growth of rational knowledge the anthropomorphic ele ments in the interpretation of natural phenomena have gradually been eliminated, and a certain amount of suspicion has fallen upon the concept of causality. Some scientists, indeed, have gone so far as to reject it altogether from the realm of science. How this has come about will be explained presently. But it may be stated at once that this extreme attitude seems to be unwarranted, even if we admit the importance of checking one's conception of the causal relationship so as to purge it of anthropomorphic sugges tions when applied to inanimate natural phenomena. Except among believers in magic, at the one extreme, and among thor ough-going sceptics, at the other extreme, it is usually assumed, either explicitly or at least implicitly, that every event has a cause, and that the same kind of cause has the same kind of effect. This assumption is commonly known as the Postulate or Principle of Universal Causation.
The Rationale of the Concept of Causality.—Let the at tempt be made to dispense with the idea of causal connection. The resulting view of the world would be one of a mere sequence of disconnected phenomena. Now, some people are quite content to regard the world in that way—to view the ever-changing phe nomena of nature as a mere sequence of new happenings in which each successive stage is in no sense the outcome of the preceding stage, but a new creation so to say. In a sense this was a favour ite thought of certain scholastics, and even Descartes shared this view. Most people, however, find such a world of disconnected changes, or rather displacements, theoretically unintelligible and practically bewildering. Even the supporters of the aforemen tioned view of incessant new creations could not entirely abandon the conception of causality. For they regarded God as the Creator (or Cause) of each successive creation in the sequence of mutually disconnected events. But the thought of such supernatural inter ference at every moment in the flow of events is not likely to ap peal to many men of science. Even on religious grounds some people would object to the conception of a world, or rather of in numerable worlds, so ill-constructed by the Maker as to have to be scrapped and replaced every moment. It seems to be more satisfying to human intelligence, and more in accordance with human experience, to suppose an orderly continuity in each se quence of changes. And the causal concept gives expression to this implicit faith in the connected continuity of events. The scientific conception of the conservation of matter or energy is prompted very largely by the same kind of consideration, namely, the belief that there are no phenomena arising suddenly out of nothing as it were, but that in some sense each event is the out come of preceding events, that each event is in fact only a new manifestation of the matter or energy of some preceding event or events. The rationale or logical motive of the concept of cau sality is, in short, to be found in the effort to see orderly continuity in the world of reality. And the sense of, or feeling for, continuity may itself be derived psychologically from man's consciousness of his own continuity under normal conditions.
The Inferential Character of Causal Connections.—The causal relation between events is not something that can be per ceived by means of the senses. What we perceive is sequence of events ; and it is from their sequence that we feel justified in in ferring their causal connection, provided certain conditions are satisfied (for these conditions see the article SCIENTIFIC METH ODS). The inferential character of our beliefs in causal connections exposes them to adverse criticisms of an easy kind. It may be argued, indeed it has been argued, that the inference to causal connection may be wrong, or that at best it is highly specu lative, so why not confine ourselves to the description of the bare sequence and ignore the question of causation? Such, for instance, was the view of Hume (q.v.), who contended that the alleged causal necessity in the sequence of the so-called causes and effects is just the hypostasis or projection of our habit of expecting cer tain consequents to follow certain antecedents merely because we had observed those sequences on previous occasions. It was largely in consequence of Hume's criticism that Kant concluded that causality is a category, that is, one of the ultimate a priori forms in which the understanding spontaneously orders its experiences (see CATEGORY)-something that is not derived from experience, but on the contrary is required to make orderly experience itself possible. It is noteworthy that Hume's attempt to explain away causality made use of this very category. For if there were no causal connection between the repeated observation of a certain sequence and the formation of a corresponding habit of expecta tion, Hume's adverse criticism of causality would have no basis in fact. Moreover, if Hume were taken literally we should have no ground for supposing any connection between his thoughts and his utterances, and so could not surmise what he really thought about causality or anything else. Common sense revolts against the at tempt to reduce causality to bare sequence. The attempts offend the active nature of man. Moreover, not every sequence is a causal sequence. Many beliefs that common sense condemns as superstitious are beliefs that result from an inability to distin guish between mere sequence and connection, so that if one event follows another (say, illness or death after being one of a party of thirteen) it is regarded as its effect. At the stage of logical re flection this slovenly way of thinking is condemned as the fallacy post hoc, ergo propter hoc (after this, therefore because of it).
Cause and Law.—Prompted partly by Hume's criticism, partly by Kant's apparently subjective interpretation of causality, and partly by the anthropomorphic origin of the conception of causa tion, some modern thinkers (Helmholtz, Mach, Pearson and others) have urged that science should discard it in favour of the concept of law. This movement is intimately connected with the tendency to make science purely descriptive without any pretence to be explanatory. The causal concept, it is urged, is an explan atory concept with a tincture of fetishism about it, why not con fine the business of science to the discovery of descriptive laws expressing uniform sequences, without pretending to explain these by reference to alleged causes? This trend of thought fits in very well with the main tendency of the more exact sciences in modern times. Under the influence of Copernicus, Galilei, Des cartes and Newton the aim of the physical sciences has come to be regarded as that of discovering descriptive equations expressing quantitative correlations of phenomena. Correlated phenomena are treated like mathematical functions. Causal connections tend to be ignored, in fact everything tends to be ignored that cannot be expressed in equations. This movement is really a legacy from ancient Pythagoreanism, which identified the essence of things with numbers. That philosophy has indeed been abandoned long since, but its consequences have been retained. And this notwith standing the growing realization that mathematical equations, after all, tell us extremely little about the real nature of things, apart from their comparatively external quantitative correlations. So marked is this tendency to let equations supplant causal connec tions that it has actually been urged that there is no good reason for the customary restriction of the term cause to antecedents only, and of the term effect to consequents only, seeing that ante cedents and consequents are mutually inferable. This is to save the name and kill the meaning of cause—causality is not the same as law or uniformity. It may be found in unique events (such as the biographer and the historian are mostly concerned with) that are not formulated in laws at all. On the other hand, there are laws, even laws of sequence, that are either not causal at all (say, the sequence of a mathematical progression) or at least are not directly causal (say, the sequence of day and night, or of the seasons). Even when expressible in laws or uniformities of se quence, the causal connection is something more than the bare uniformity of sequence. No doubt it is objectionable to introduce anthropomorphism or animism into the study of inanimate phe nomena. No doubt it is well to remember the obstruction to science caused by "substantial forms," etc. But caution may be carried too far. After all, even human beings are natural phenom ena, and their experiences may be used as a clue to the interpreta tion of nature, provided due care is exercised. It would certainly be extravagant to project into the causal sequences of inanimate phenomena anything analogous to the sense of effort or of con straint that is experienced in human activity or passivity respec tively. But that is no reason for discarding causality altogether. Carried through consistently, this can only end in the conception of the world as a series of independent miracles—a view even more irrational than the anthropomorphism which it is intended to correct. The principle of conservation of matter or energy would lose all significance without the idea of causal continuity, according to which certain successive events not only follow, but follow from one another. In fact, mere laws of sequence are only intelligible in the last resort, when they can be shown to result from direct or indirect causal connections.
A word may be added about Plurality of Causes, or the view that the same kind of effect may in different instances be produced by different kinds of causes. In a general way different causes may produce results that may serve the same practical purpose—light, warmth, satisfaction, death, etc., may be produced in a large vari ety of ways, and yet make no serious practical difference. Strictly speaking, however, the effect is always different in some way when the cause is different in any way. Although death, e.g., may result from any of the thousand ills that flesh is heir to, and it may make little or no practical difference which of them actually caused it, yet when the occasion requires it coroners' inquests are held in the just belief that differences in the cause of death can be inferred from differences in the state of the dead body. So that, strictly speaking, not only does the same cause always produce the same effect, but the same effect can only be produced by one kind of cause.