Science

Where can I read something about the difference between explanation and justification? How would you put this difference in a few words?

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A scientific explanation specifies the reason *why* some fact is the case or (or the reason why some event came about). A justification specifies someone's good reason for believing in the truth of some claim.

For example, my justification for believing that the dinosaurs went extinct is that I have seen no dinosaurs around, and I have never heard any reports of living dinosaurs, but I have seen all of those fossils, and scientists whom I trust say that they have good evidence that dinosaurs once roamed the earth. But that's not the reason why the dinosaurs went extinct. The explanation (according to our best current theories) involved a large object crashing into the earth.

Notice that my justification for believing that the dinosaurs went extinct does not concern my knowledge of the reason why they went extinct.

Notice also that I could be justified in believing in some claim even if, as a matter of fact, the claim is false. A physician, for instance, might be justified in believing that her patient Jones has phenylketonuria when, in fact, Jones does not; perhaps Jones actually has some other disease that the physician has never heard of. The physician can be justified in believing in p even if p is actually false. In contrast, if p is false, then there is no explanation of p's truth; there is no reason why p is true if, in fact, p is false.

For a place to read more about this, see Carl G. Hempel, "The Philosophy of Natural Science," Englewood Cliffs, NJ: Prentice-Hall, 1966.

When you ask for an explanation, you usually already have a justification. You want something more -- understanding -- which is what an explanation provides. Thus when you ask why the same side of the moon always faces the earth, you already know that it does, but you do not understand why. Much of the work in the philosophy of explanation can be seen as attempts to say what takes you from knowledge to understanding.

(By the way, the reason the same side of the moon always faces the earth is not because the moon is not spinning. In order for the same side of the moon always to face the earth, the moon has to spin around itself with exactly the same period as the period it takes the moon to orbit around the earth. Spooky, eh?)

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