Hypothesis and the So-What Criterion in Science
Any theory in science is based on certain fundamental assumptions which one agrees to accept provisionally. These assumptions constitute the hypotheses of the theory. Thus, a hypothesis is invariably the starting point of a theory in science. The term is derived from the Greek, hypo: under, and tithenia: to put. So the word means that which is put under. [We may note in passing that Latin words for under: sub, and to put: ponere, have given rise to the words, supposition and suppository.]
A hypothesis is usually succinct in expression, concise as a formula, and quite general as a statement. In physics, it has invariably a mathematical component. By itself, a hypothesis is of no interest in science. It is only when one explores its consequences that its significance, if any, will become apparent. The exploration of the consequences of a hypothesis is what constitutes a theory in science.
There is much truth in the quip, attributed to Edward Teller: “A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is a novel suggestion that no one wants to believe. It is guilty, until found effective. “
Usually, though not always, a hypothesis in science refers to some aspect of the physical world that is not directly amenable to observations. Thus the wave theory of light is based on the hypothesis that light consists of undulatory (wave-like) disturbances that propagate through space. This is not a property of light that can be directly perceived, but its logical consequences can be observed. Similarly, the kinetic theory of gases rests on the hypothesis that a gas is made up of extremely small billiard-ball-like entities (molecules) which move and collide at random. It is impossible to observe molecules and their motions directly, but the theory brings out several observable consequences of such a state of affairs. These have been amply verified. Hence the hypothesis has been accepted as true. The validity of a hypothesis depends on the verifiability of its consequences as brought out by the theory that is based on it.
The formulation of a fruitful hypotheses is in some ways more significant than the discovery of an experimental fact in that whereas the observable fact is within our perceptual reach, the explanatory hypothesis is a discovery by a penetrating mind. “Facts would be barren,” wrote Henri Poincaré, “if there were not minds capable of selecting between them and distinguishing those which have something hidden behind them and recognizing what is hidden – minds which, behind the bare fact, can detect the soul of the fact.” Indeed, it is only through the process of hypothesizing that we have been able to extend the frontiers of human knowledge. As Enrico Cantore stated, “A tentative interpretation of observational data is the only way open to genuine science, no matter how abundant observational data may be.
One is allowed to make any hypothesis in science. But if the hypothesis is to be of any interest to the scientific community, it must come out successfully when subjected to what may be called the so-what criterion. According to this, when a hypothesis is formulated, it must answer the question, “So what?” It is the answer or answers to this question that will determine the importance, usefulness, relevance, and consequent acceptability of the proposed hypothesis. This criterion is almost self-evident to the working scientist. But it is often lost sight of in debates between science and other fields of human endeavor.
Consider the following two statements, in both of which the idea of light has been introduced:
“God said, Let there be light, and there was light.”
“Light is made up of electromagnetic vibrations propagated through space with a finite velocity.”
Let us consider for a moment the two statements to be as yet unconfirmed features of light. From the second statement we can draw a number of conclusions whose correctness or otherwise may be checked by direct observations, and through well defined experimental procedures. Thus, if one asked, “So what?” when this statement is made, a number of answers may be given.
On the other hand, hardly any consequence of empirical interest follows from the first statement. This does not necessarily imply that it is false or incorrect. Indeed it may well be that in some deeper sense it is fundamentally truer than the second statement. For, our views as to the ultimate nature of light may still change drastically in the course of the next few centuries, while a Supreme Being could well have created the universe, and have imposed light in it by a mere command. But the point is that unless a hypothesis – which, we recall, is a statement about an unperceived aspect of the world – leads to observable consequences, it is of little value or relevance to the scientific enterprise. It is in this sense that the first statement is not scientific while the second is.