Why This Makes Divine Justice a Meaningful Claim

The doctrine that reason can know good and evil independently of revelation is not an isolated position within Mutazili thought; it is what makes the parallel doctrine of adl, divine justice, a claim with actual content rather than an empty label. If good and evil had no standard except whatever God happens to command, then calling God just would say nothing beyond that God does what he does, since justice would simply be defined as divine action rather than measured against it. Only if reason has independent access to a real standard of good and evil can the statement that God is just function as a genuine claim, one that could in principle be false, rather than a tautology true by definition. This is why the two Mutazili principles travelled together into Zaydi, Twelver and Ismaili theology as a linked pair rather than as separate, independent commitments: divine justice requires an external standard for justice to be measured against, and the doctrine that good and evil are knowable by reason is precisely what supplies that standard. The same pairing put Mutazili theology at odds with the later Ashari doctrine of kasb, acquisition, which held that God originates every human act and a person merely acquires it, a position Mutazili thinkers rejected as incompatible with the genuine authorship adl requires.