The causal relation between a cause and its effect is an...

The causal relation between a cause and its effect is an essential and unalterable relation; that is, the existence of the effect is essentially dependent on the existence of the efficient cause, and it is impossible that the positions of cause and effect should be changed so that the existence of the cause should be dependent on the existence of the effect. So, it is impossible that an effect should be produced by something on which it is not dependent.

The causal relation is also a necessary relation, and it is impossible for the existential dependency of the effect on the cause to vanish, so that the effect could occur without the cause. Hence, the possibility of being an effect is equal to its necessity.

In other words, the causal relation between two existents can never be considered to be merely possible ( imkān khāṣṣ , the negation of the necessity of the terms of the relation), so that it is possible for one of the two existents both to be and not to be an effect of the other with neither of them being necessary.

So, if it is not impossible for one thing to be the effect of another, it will be necessary for it to be the effect of the other, and without the other it would not come into existence. On the other hand, in the discussions of cause and effect it was established that the criterion for being an effect is weakness of existence.

Therefore, this supposition will be necessary wherever a more perfect and more powerful existent can be supposed, so that the weaker existent may be considered to radiate from its existence, not being independent of it.

By attending to these two premises, the above-mentioned doctrine may be obtained as follows: If we suppose that there are a number of existents each of which is more powerful than another, so that the former may be considered the cause of the existence of the latter; in other words, if a special gradation is posited among them, then each of the more powerful existents will be at a prior level to the weaker existents, and necessarily will be the cause in relation to them, until one arrives at an existent for which it is impossible to suppose a more perfect one, and which cannot possibly be the effect of any of the other existents.

According to this doctrine, the existence of intellectual substance, which is more perfect than other substances and can be the cause for their existences, is established. This will be an intermediary between the level of infinite intensity of existence (i.e.