In short, the psychological necessity of believing in causality lies in the impossibility of imagining a process without a purpose: but of course this says nothing concerning truth or untruth (the justification of such a belief)! The belief in causæ collapses with the belief in τέλει (against Spinoza and his causationism).
628.
It is an illusion to suppose that something is known, when all we have is a mathematical formula of what has happened; it is only characterised, described; no more!
629.
If I bring a regularly recurring phenomenon into a formula, I have facilitated and shortened my task of characterising the whole phenomenon, etc. But I have not thereby ascertained a "law," I have only replied to the question: How is it that something recurs here? It is a supposition that the formula corresponds to a complex of really unknown forces and the discharge of forces; it is pure mythology to suppose that forces here obey a law, so that, as the result of their obedience, we have the same phenomenon every time.
630.
I take good care not to speak of chemical "laws": to do so savours of morality. It is much more a question of establishing certain relations of power: the stronger becomes master of the weaker, in so far as the latter cannot maintain its degree of independence,—here there is no pity, no quarter, and, still less, any observance of "law."
631.
The unalterable sequence of certain phenomena does not prove any "law," but a relation of power between two or more forces. To say, "But it is precisely this relation that remains the same!" is no better than saying, "One and the same force cannot be another force."—It is not a matter of sequence, but a matter of interdependence, a process in which the procession of moments do not determine each other after the manner of cause and effect....
The separation of the "action" from the "agent"; of the phenomenon from the worker of that phenomenon: of the process from one that is not process, but lasting, substance, thing, body, soul, etc.; the attempt to understand a life as a sort of shifting of things and a changing of places; of a sort of "being" or stable entity: this ancient mythology established the belief in "cause and effect," once it had found a lasting form in the functions of speech and grammar.