What Is an Explanation?

Explanations are not arguments

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An explanation is not an argument. Whereas an argument is a series of statements designed to support or establish the truth of an idea, an explanation is a series of statements designed to shed light on some event that is already accepted as a matter of fact.

Explanandum and Explanans

Technically, an explanation is composed of two parts: the explanandum and the explanans. The explanandum is the event or phenomenon or thing which is supposed to be explained.

The explanans is the series of statements which is supposed to do the actual explaining.

Here is an example:

  • Smoke appears because of fire: a combination of flammable material, oxygen, and sufficient heat.

The phrase “smoke appears” is the explanandum and the phrase “fire: a combination of flammable material, oxygen, and sufficient heat” is the explanans. In fact, this explanans itself consists of an entire explanation — “fire” plus the reason why fires happen.

This is not an argument because no one disputes the idea that “smoke appears.” We already agree that smoke exists and are simply looking to find out why. Were someone to dispute the existence of smoke, we would have to create an argument to establish the truth of smoke.

Although none of this seems very enlightening, the fact of the matter is that many people don’t entirely realize what goes into a good explanation. Compare the above example with this:

  • Smoke appears because of smoke-producing events.

A Good Explanation

This is not a valid explanation, but why? Because it provides us with no new information. We have not learned anything from it because the supposed explanans is simply a restatement of the explanandum: the appearance of smoke. A good explanation is something which provides new information in the explandum which does not appear in the explans.

A good explanation is something from which we can.

In the first example above, we are provided with new information: fire and what causes a fire. Because of that, we learned something new which we did not know from simply examining the explanandum.

Unfortunately, too many “explanations” we see take a form more like #2 than like #1. It usually isn’t quite so obvious as these examples here, but if you examine them closely, you will find that the explanans is little more than a restatement of the explanandum, with no new information added.