Compare the two cases: 1. “How do you know that he has pains?” ‒ ‒ ‒ “Because I hear him moan”. 2. “How do you know that you have pains?” ‒ ‒ ‒ “Because I feel them”. But “I feel them” means the same as “I have them”. Therefore this was no explanation at all. That, however, in my answer I am inclined to stress the word “feel” and not the word “I” indicates that I don't wish to pick out one person (from amongst different persons).