On Philosophy

November 25, 2006

The Importance of Explanations

Filed under: Epistemology — Peter @ 2:04 am

Let us assume for the moment that the quality of a theory should be judged based on the accuracy of its predictions, and not, for example, on how well it explains the world. We can certainly envision doing science without explanations. In such a world we would simply observe a regularity in some phenomenon and make the prediction that events would continue in basically the same fashion (of course we would have to conduct some statistical analysis on the data as well, in order to make the theory accurate). And if observations confirm that prediction then it would be a good theory, and just as good as a theory that made the same predictions but also explained why the regularity existed. What role then do explanations play?

Well, when theorizing about a single phenomenon, explanations may not really be necessary. When we study a single case there is really no basis for choosing one explanation over another. Imagine studying only the decay of one single isotope into another. We can easily conceive of several possible explanations. One explanation might invoke forces within the nucleus, one might appeal to tiny gnomes, and one might describe the decay as simply a fundamental property of the atoms. Without investigating other phenomena there is no real way to distinguish between them. And since atomic decay occurs in a fairly regular way all of these theories could be equally accurate in making predictions, so why should we care?

But science cannot usefully progress by studying isolated phenomena. There are simply too many starting points from which events may develop to study each one in isolation. What we need then are theories that can make accurate predictions in a wide range of cases. If we are presented with such a theory we can test it in a number of different cases (although not in all cases), and if it proves reliable it is reasonable to act under the working assumption that it is reliable in all cases, until proven otherwise. Such theories are the goal of science, not predications about isolated phenomena.

A vital step in this process is developing candidate theories that make predictions for a wide range of situations. Of the possible explanations of atomic decay I mentioned above only the appeal to forces within the nucleus has the possibility to be extended to other cases. Appealing to gnomes, or simply assuming that atomic decay is a fundamental property, doesn’t give us a basis for predicting the decay of other isotopes. These other explanations can’t be extended to the more general case simply because, unlike the case of the single isotope, we simply can’t make enough observations to develop possible laws of decay directly from them. Appealing to gnomes only worked because we could come up with exact predictions based on our observations alone, an appeal to gnomes without such data simply has no basis for making predictions. When considering isotopes in general there are simply too many cases to come up with laws from the observations alone. Even though we should make as many observations as we can in order to construct better candidate theories we simply can’t look at all the possibilities.

This is where the need for an explanation arises. We can construct possible explanations based on the limited observations we have made, and on the basis of our proposed explanation make predictions for the cases that we have not observed. Now we could come up with general laws without explanations, but without observations covering every possibility we would be essentially shooting in the dark, as far as the unobserved cases were concerned. So even if explanations aren’t strictly necessary for a theory to be successful (in the sense of accurate) they are needed to arrive at the broad theories that are actually useful.

You can read a related post here.



  1. I’m unclear on what you mean by “explanation”.

    In the case of the natural sciences, following in the tradition of logical positivism, a scientific explanation is exactly parallel to a scientific prediction. In both cases, one simply states the initial conditions and the relevant laws. Thus, to predict how far a ball will fall in 3 seconds, we simply plug in 3s and 9.8m/s^2 in the equation (or law) d=1/2at^2. In the case of an explanation we are asking why a ball fell X meters when it dropped for 3 seconds. Again, we simply state the initial conditions and the law. In this case there is no distinction between prediction and explanation.

    In the case of social science, philosophers disagree about whether they should be seeking causal explanations of the sort mentioned above or rather non-causal, interpretive explanations which are aimed at making action intelligible. In this case there is a serious disagreement for in the case of the interpretationalists an explanation necessarily includes intentional terms such as beliefs and desires. From this it should be plain that an interpretationalist explanation in the natural sciences is surely inappropriate.

    Finally, I wonder if you mean by “explanation” the reduction of one law to a more basic one, for example the reduction of chemical laws to the relevant underlying physical laws. This, however, seems to be a case of explaining laws rather than phenomena, for we say that a chemical law is explained by such and such physical laws in that the former is the deductive consequence of the latter. Again, however, we see the close parallel between prediction and explanation, for deduction is the source of both explanation and prediction in logical positivism.

    I guess I just don’t know what you mean by an explanation which is distinct from a prediction in the case of the natural sciences.

    Comment by Jeff G — November 25, 2006 @ 9:51 am

  2. An explanation is something that answers the question: “why?”

    Comment by Peter — November 25, 2006 @ 4:35 pm

  3. Don’t you think “why?” is a little ambiguous? I mean each of Aristotle’s four causes could be given as an answer to “why?”

    Comment by Jeff G — November 25, 2006 @ 10:38 pm

  4. Yes, there are many ways to construct an explanation. I didn’t even attempt to go into them here, for good reason. Obviously the only explanations that will work, in the sense of being able to make predictions about related cases, are usually going to be what aristotle called material causes or formal causes, but that is a different can of worms.

    Comment by Peter — November 25, 2006 @ 11:16 pm

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