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De Motu, Section Sixty-eight

29 September, 2015 - 16:50

Let us lay down that the new motion in the body struck is conserved either by the natural force by reason of which any body persists in its own uniform state of motion or of rest, or by the impressed force, received (while the percussion lasts) into the body struck, and there remaining; it will be the same in fact, the difference existing only in name. Simi- larly when the striking moveable body loses motion, and the struck body acquires it, it is not worth disputing whether the acquired motion is numerically the same as the motion lost; the discussion would lead into metaphysical and even verbal minutiae about identity. And so it comes to the same thing, whether we say that motion passes from the striker to the struck, or that motion is generated de novo (anew) in the struck, and is destroyed in the striker. In either cases it is understood that one body loses motion, the other acquires it, and besides that, nothing.

  1. According to De Motu, Section Thirty-five, what is the true business of natural science? Of philosophy?
  2. What is gravity? Is there a sense in which even asking this question is a mistake?
  3. What problem is Berkeley discussing in De Motu, Section Sixty-eight? How does his handling of it differ from Locke’s?