This is a summary of the argument the shaykh (rahimahu Allah) gives against occasionalism at al-Shifa’; Ilahiyyat IV.2:
We evidently know that
Burning regularly proceeds from fire when it is put into contact with cotton
Now the question is: why does this happen? The answer must be one of the following: either the occurrence of burning is (1) due to the fact that fire is a body, or (2) it’s due to some factor, F, additional to fire’s being a body, or (3) it’s due to some separate i.e., non-corporeal, causal agent, G, involved in the event.
Option (1) can’t be the case. For otherwise, burning should then proceed regularly from any given body that comes in contact with cotton; for qua bodies, all bodies are equivalent. But, it clearly doesn’t, as experience testifies.
If option (2) is true, this is the conclusion sought (maṭlūb). For whatever this additional factor F is, we call it a ‘power’ (quwwa). Hence, fire would then burn the cotton in virtue of a power F that it has. With this, occasionalism is false.
If option (3), fire regularly serves as an intermediary in G’s production of burning either (3.1) because of the fact that fire is a body, or (3.2) due to some factor, F, in fire other than its being a body, or (3.3) due to some factor, F*, in G.
If (3.1), then any other body should equally regularly mediate G’s production of burning from it; for, again, qua bodies, all bodies are equal and so are equally up to the task. However, as experience shows, it is fire that regularly does the job, not e.g., snow, or any other body.
If (3.2), this again is the conclusion sought (maṭlūb); for F would then be a power. And hence, occasionalism is false.
As for option (3.3), this factor, F*, in G is either (3.3.a) such that it of itself necessitates the occurrence of burning from fire or (3.3.b) is such that it specifies that occurrence on the basis of a volition.
If (3.3.a), then F* regularly necessitates the occurrence of burning from fire, again, either because (i) fire is the body that it is or (ii) because of something that it has additional to the fact that it is a body.
It should be clear by now why (i) can’t be the case and why (ii) leads to the desired conclusion (maṭlūb).
That leaves option (3.3.b). Here, two options present themselves for explaining the production from burning by G, from fire, on the basis of an act of volition: either (3.3.b.i) G wills the occurrence of burning from the fire due some reason having to do with the fire, or (3.3.b.ii) G does it randomly and arbitrarily.
If (3.3.b.ii) randomly, then, contra our initial premise, burning would not regularly proceed from fire upon its contact with cotton. For randomness and regularity are opposed. But, it clearly does – as experience testifies. Hence, (3.3.b.ii) is false.
Therefore, option (3.3.b.i) remains; G wills burning from fire due to some reason having to do with fire. And whatever that reason is, its basis in fire we call a power, F, belonging to fire. Thus, G wills burning from fire because of power F in fire.
Now, what’s the relation between F in the fire and the burning that occurs upon fire’s contact with cotton? The relation is either one of:
- necessitation (i.e., F necessitates the occurrence of the burning), or
- randomness (i.e., the connection between F and burning is by chance)
If (2), then we would not observe the regular occurrence of burning from fire upon contact with cotton. But, we clearly do. Hence, (2) can’t be true.
Therefore, (1) is the case. But if (1), this is just the conclusion sought (maṭlūb): F, a power in fire, causally necessitates burning upon contact with cotton. And therefore, occasionalism is false.