It is worth noting the subtle point that according to the...

It is worth noting the subtle point that according to the fundamentality of existence, motion must be related to existence as an analytic accident, and the relating of it to the whatness of a substance or accident is an accidental relation. Arguments for the Existence of Substantial Motion Ṣadr al-Muta’allihīn offered three lines of argument to establish substantial motion. The first argument for substantial motion has two premises.

One is that accidental changes in a thing are the effects of the substantial nature of that thing. The second premise is that the natural cause of motion must be a moving thing. From this it is concluded that a substance which is the cause of motion in accidents must be a moving thing.

As for the first premise, this is the famous principle indicated in the previous lesson, that is, the proximate and immediate agent of all motions is nature, and no motion can be directly related to an immaterial agent. As for the second premise, it may be further explained that if the proximate and immediate cause of an effect were a stationary object, its result would also be a stationary.

In order to make this easier to understand, the following example may be used: if a lamp were in a fixed place the light which radiates from it would illuminate all within a specific radius, but if the lamp were in motion, the extent of its illumination would gradually advance. Hence, the process of moving accidents which advance in the realm of time shows that their cause also is in process along with them.

Perhaps it will be asked, if the nature of a substance is essentially in motion, then why are its effects, which are accidents, sometimes without motion? And why cannot the immobility of accidents be reason for the immobility of the nature of a substance? These question can be answered as follows.

The nature of a substance is not a complete cause of motion, rather, its effectiveness depends on specific conditions whose satisfaction brings about motions in accidents, and motion is an action which requires a natural agent, even if the agent is not the complete cause of its occurrence. Immobility, to the contrary, is a negative thing (the absence of motion), and cannot be considered to be an action in need of an agent.

On the other hand, it may be asked whether the proponents of substantial motion are not forced to relate substantial motion to immaterial agents, which are fixed, unchangeable and devoid of motion.