the willing agent under any circumstances. A resolute will without power does not bring its object into existence, whereas a resolute will accompanied by complete power necessarily entails the existence of its object. Thus, if one of the two joint agents possessed complete power and complete will, the effect would necessarily be produced by it alone. Yet its being produced by that agent alone precludes its being produced by the other. This entails two contradictories being true together: the effect being produced by that agent alone and not being produced by it alone, and that agent being both an agent and not an agent. This is plainly impossible.

This mutual exclusion does not mean that each of the two agents prevents the other from acting, as when one is said to will to move a body while the other wills to keep it still, or one wills to cause a person’s death while the other wills to bring him to life. Rather, it is an intrinsic mutual exclusion: two partners, each possessing complete power and will, cannot jointly produce an effect over which each has complete power and which each fully wills. For whoever has complete power over something and fully wills it must necessarily produce the effect alone. If the other is likewise, the effect must necessarily be produced by it. These two consequences follow one another and exclude one another, since affirmation precludes negation and negation precludes affirmation, in an intrinsic relation of mutual exclusion and contradiction.

It is thus clear that acting jointly necessarily entails a deficiency in the partner’s power itself. If two agents are supposed to will some particular thing, one of two cases must obtain:

Either the effect produced by one is not the effect produced by the other, but each independently produces part of the effect.