Cause and Effect in Experimental Research

Debate on the relation between cause and effect, causality, as it is known in philosophy, is more than two hundred years old and was prominently projected by Hume, a British philosopher. Light­ning and thunder follow a sequence, lightning before thunder. In normal commonsense language, we may say that a particular lightning “caused” the subsequent thunder. Hume’s argument against such a statement runs somewhat like this: Our knowledge of the external world is derived only through experience, which in turn is based on sense perceptions. (This brand of philosophy is known as empiricism). Lightning is a sense perception of the eye; thunder is another perception of the ear. In between, we did not perceive anything like “cause” because it simply did not exist. Fur­ther, thunder following lightning can be attributed to sound trav­eling more slowly than light. Therefore, our idea of sequence— lightning first, then thunder—is not quite correct either. Our say­ing that lightning caused thunder is thus only a way of speaking, a custom, nothing that “necessarily” follows from thought. Mathe­matical relations that “necessarily” follow from thought, free of perceptions, and, equally, experiments that can be directly con­ducted without relying on sense perceptions do not need any (fic­titious?) “cause,” hence, are philosophically supportable.

Since Hume, a lot of exposition on, as well as debate for and against, causality abounds in philosophy. The objection against “cause” was later renewed by Russell,¹ with the determination to “extrude it [the word ‘cause’] from philosophical vocabulary.” Russell’s main objection seems to center on the time element between cause and effect, and he seems to object less if the cause- effect relation is understood to be only probable, and even when the probability is very high, Russell argues, it is not a “necessary” relation. He gives an example: “Striking a match will be the cause of its igniting in spite of the fact that some matches are damp and fail to ignite.”

In the context of experimental research, however, the notion— even if it is only a notion—of a cause-effect relation has survived to this day, leaving aside the raging battle in the world of philosophy. In experimental research, wherein confirmation, prediction, and control within certain domains of nature are the purposes, the idea of cause is not only useful but necessary to analyze and express the events in ordinary, commonsense language. Presence or absence of current in the connecting chord makes the differ­ence between the fan working as expected and not working. Cur­rent as an agent of action is the cause necessary to expect the effect, the functioning of the fan. Using the concept of cause between or among events is common in experimental research. The invariant relation between two events A and B, meaning that when A happens, B happens also, and when A does not happen, B does not happen either, is sufficient to say that A and B are causally related. If A always happens before B, there is a temporal relation as well. In such circumstances, we say that A is the cause of B, or simply, A causes B. In some circumstances, the temporal relation may not be necessary for the causal connection. The falling stone acquires acceleration because of earth’s gravity. But whether grav­ity happened before acceleration is a question leading to unneces­sary debate. This idea, from time to time, has raised its head as an objection against “action at a distance,” as implied by the Theory of Gravitation. Suffice it to say that gravity is the cause of acceler­ation, or gravity causes acceleration.

Source: Srinagesh K (2005), The Principles of Experimental Research, Butterworth-Heinemann; 1st edition.