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Thought experiments (henceforth, "TE's") in science take the form of short narratives in which various experimental procedures are described. The competent reader understands that these procedures have not been, and usually could not (for some appropriate modality) be, enacted. She is invited, however, to imagine or make believe that these procedures are enacted and to conclude that certain consequences would ensue, where this is taken to bear upon a more general question which is the topic of the TE. Perhaps the most famous example of such a device is Galileo's "Tower" TE which aimed both to refute the standing Aristotelean account of the behavior of falling bodies, and to establish the alternative account favored by Galileo himself. The Aristotelean account held that the speed at which a body falls is directly proportional to its weight. Galileo asks us to imagine that we take two bodies, one heavy [H] and one light [L], to the top of a high tower. We strap the bodies together and drop the resulting object [H+L] from the tower. The Aristotelean is then committed to two contradictory claims. First, since [H+L] is heavier than [H], it should fall faster than H. On the other hand, since [L] falls more slowly than [H] it should retard the fall of [H], and since [H] falls more quickly than [L] it should accelerate the fall of [L]. So [H+L] should fall at a speed somewhere between the rate of fall of [H] and the rate of fall of [L]. Since the Aristotelean view leads to an absurdity—that [H+L] will fall both more quickly and more slowly than [H]-rate of fall must be independent of weight. Given this "intermediate" conclusion, Galileo further concludes that (if we remove the resistance of a medium) all bodies fall at the same rate.¹

DOI: 10.1007/978-90-481-3851-7_4

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