Full Idea
It is true that pain does not resemble the movement of a pin; but it might thoroughly resemble the motions which the pin causes in our body, and it might resemble them in the soul; and I have not the least doubt that it does.
Gist of Idea
A pain doesn't resemble the movement of a pin, but it resembles the bodily movement pins cause
Source
Gottfried Leibniz (New Essays on Human Understanding [1704], 2.08)
Book Reference
Leibniz,Gottfried: 'New Essays on Human Understanding', ed/tr. Remnant/Bennett [CUP 1996], p.132
A Reaction
He may not have the least doubt, but the rest of us do, I should think. Try as I will, I cannot see any resemblance between pain and a motion. What feeling does a pendulum resemble?