By capability is meant the physical or psychological power of performing an act.

By responsibility is meant the moral (as distinct from the physical) necessity of performing an act.

Physical or bodily powers incapable of moral necessity are incapable of responsibility.

A power that is incapable of an act may be responsible for an act, if it has (i) physical, (2) psychological, or (3) moral power over another power which is capable of the act.

(1) Physical? The human will is not capable of cutting a human throat. A knife is capable of cutting a human throat. But a human will using a knife is responsible for cutting a human throat. In other words a human will has not the capability but has the responsibility of cutting or not cutting a human throat. .

(2) Psychological. The feet have the capability of walking but not of hearing or of seeing. The ears have the capability of hearing but not of seeing or of walking. The eyes have the capability of seeing but not of walking or of hearing. The human will has the capability neither of walking nor hearing nor seeing.

Now the feet which have the capability of walking are not responsible for walking. The ears which have the capability of hearing are not responsible for hearing. The eyes which have the capability of seeing are not responsible for seeing.

But the human will which cannot walk nor hear nor see can move (or not move) the feet to walk, the ear to hear, the eye to see.

Therefore the human will which has not the capability of walking, hearing seeing, has the responsibility of walking, hearing, seeing.