With regard to the fact that not just anything can bring...

With regard to the fact that not just anything can bring about any kind of change, it is summarily obtained that some sort of relation and homogeneity is also necessary between such causes and effects. However, the characteristics of this sort of homogeneity cannot be established by rational proof, rather, it is only through experience that one can discern what sort of things can be the source of what changes, and under what conditions and with the aid of what things these changes are produced.

For example, reason, by means of conceptual analysis, would never be able to discover whether water is simple or is composed of other elements, and if the latter, of what and how many elements it is composed. What conditions are necessary for such a composition? Are these supposed conditions replaceable or not?

Hence, it is only by means of experience that it is possible to establish that water is composed in a special way of two elements, oxygen and hydrogen, that this composition requires a certain temperature and pressure and that an electrical current can speed the process of composition.

The Removal of a Doubt We have stated that it follows from a rational proof that every existence- giving cause must possess the perfection of its effect, for it is absurd to suppose that the granter lacks that which it grants to another.

With regard to this topic, the following problem may be raised, that an implication of this principle is that existence-giving agents have material existences and their perfections, while an existence-giving agent can only be an immaterial existent which does not have matter or the specific attributes of matter. So how can something emanate that which it itself does not possess?

The answer to this problem is that what is meant by possessing the perfection of an effect is having a more perfect and higher level than the existence of the effect, such that the existence of the effect is considered to be the radiance of the cause, not that the limits of the existence of the effect are exactly preserved in the cause, and not that the cause has the same whatness as the effect.

It is clear that the greater perfection of the existence of the cause than the level of the existence of the effect is not compatible with their whatish unity.