There are actually many possible causes.
Impotence is a very sensitive subject.
Impotence is the inability for a male to get or maintain an erection. To say the least this condition would be very disconcerting for any male. Especially if he had previously had normal arousal and sexual relations. Unfortunately, at one time or another, almost all males have or will experience this problem, and thus, somewhat normal occurance. In about half or so of the documented cases of impotence, the cause is purely physical.