facing the sun, so that its rays may be reflected upon it. If the sun is not a complete cause, their intended point is not established. Rather, it is part of the cause: it is a cause and a condition. For the rays depend both on the shining sun and on the surface upon which they are reflected. Their dependence on these two is therefore that of something conditioned upon its condition. They distinguish priority by causation from priority by nature and by condition on the grounds that what is prior as a cause entails the existence of what comes after it, whereas what is prior as a condition does not.

We have already stated that no created thing, on its own, entails the existence of something subsequent to it. His will, however, entails what He wills: whatever Allah wills comes to pass, and whatever He does not will does not come to pass. It has become clear, in the case of the rays they offer as an example, that if the sun alone were assumed to exist without anything facing it, the rays would not exist. Rather, their existence is conditional upon both the sun and what faces it; thus, these are two conditions.

Since each is a condition, a condition may or may not precede what is conditioned upon it. Undoubtedly, the wall, the earth, and the air exist before the rays; likewise, the sun exists before these rays. This is temporal priority. Yet when it is present, the rays arise, generated through the conjunction of these two sources, just as other generated things are generated from