Full Idea
I have heard it said by people whose arm or leg has been amputated that they still sensed pain in the lost limb. Thus it does not seem certain that one of my bodily members causes me pain, even though I sense pain in it.
Gist of Idea
If pain is felt in a lost limb, I cannot be certain that a felt pain exists in my real limbs
Source
René Descartes (Meditations [1641], §6.77)
Book Reference
Descartes,René: 'Discourse on Method/The Meditations', ed/tr. Sutcliffe,F.E. [Penguin 1968], p.155