Likewise, the term “causal efficacy” admits of more than one meaning. Capacity stands in relation to what it enables as a causal means does to its effect, a cause to what it causes, and a condition to what is conditional upon it. If “capacity” means the capacity recognized by the revealed law, which makes the act possible and precedes it, then it is a condition for the act, one of its causal means, and an incomplete cause of it. If, however, “capacity” means the capacity that accompanies the act and necessarily entails it, then it is a cause of the act and a sufficient causal means.

It is well known that nothing among created things is, by itself, a complete cause and sufficient causal means for events, in the sense that its existence necessarily entails their occurrence. This belongs exclusively to the will of Allah Most High: whatever Allah wills occurs, and whatever He does not will does not occur. As for created causal means—such as fire in burning, the sun in illumination, and food and drink in satisfying hunger and quenching thirst—none of these produces the event by itself. Rather, another causal means must join it. Even then, there are impediments that prevent the two from producing their effect. Thus, every causal means depends upon the presence of the requisite conditions and the absence of impediments. Nothing among created things produces anything entirely by itself.

This makes clear to you the error of the philosophizers who said:

“From one, only one proceeds.”

They drew an analogy with natural effects, such as things that are heated or cooled, and the like. This is mistaken, for heating requires two things: first, an agent, such as fire; and second, a recipient, such as a body capable of receiving heat and being burned. Otherwise, when fire comes into contact with a salamander or a ruby, it does not burn it. Likewise, the sun’s rays depend upon a body facing the sun, onto which the rays are reflected; and they are obstructed by clouds, roofs, and other