All three of our authors have an important place for both revelation and reason, but they describe the relation between the two sources of knowledge differently. The term ‘revelation’ is a convenience, but is potentially misleading. It would be better, but cumbersome, to talk about God’s deliverances through the Scriptures and the Traditions.

6.3.1 “‘Abd al-Jabbar”

Al-Jabbar makes a distinction between necessary knowledge and acquired knowledge. Necessary knowledge, unlike acquired knowledge, is known immediately and is known by all sane adult human beings. This includes knowledge from sense perceptions and rules of logic and knowledge of one’s own mental states. The most important for present purposes are certain moral truths and reliable reports. An adult with sound mind necessarily knows the evil of wrongdoing, the evil of being ungrateful to a benefactor, and the evil of lying if it is not intended to bring about benefit or to repel harm. One also knows the goodness of compassion and giving. These moral principles are the basis for rational obligations. Knowledge of reliable reports is also necessary for knowledge, and is required for religious obligation, which is a part of obligation not known by reason—like the obligation to pray and fast.

So al-Jabbar gives a kind of priority to reason over revelation. Neither revelation nor reason makes something right or wrong. But the right that revelation indicates, reason sees is instrumental towards a right that reason already knows. We know by necessary knowledge that we should choose our duty, and revelation tells us that prayer is conducive to this end. There is a difference between intrinsic wrongs and things that are wrong by relation to their consequences, such as the wrongs of the Law, which are only wrong inasmuch as they lead to the performance of a rational wrong or ceasing to perform certain duties. This does not mean, however, that revelation is redundant. One may not know, before being told, how to achieve the end in question, and one also may be insufficiently motivated.

The opponents of the Mu’tazilites tended to object that the moral principles that are supposed to be necessarily known, and so known to all sane adults, are in fact not known by all. There is, in fact, widespread disagreement. For example, the nomadic Bedouins of Arabia approve the practice of plunder. But this does not mean that there is disagreement here about the principle that injustice is prohibited; it’s just that Bedouins have a different conception of private property. But it’s hard to see that the objection from disagreement can be overcome in this way. To be sure, ‘injustice’ is named together with the wrong and so anyone who agrees that some act is unjust is going to agree that it is wrong; but the relevant disagreement is surely about what kinds of act are unjust.

So take lying. One might object that this is not something about which all sane adults agree, and indeed many of al-Jabbar’s own opponents disagreed with him, holding that it would be right to lie to save the life of a prophet. But the case of lying is anomalous here, and it may be that the operative conception of lying is already evaluatively laden. There is nothing implausible, Hare writes, about holding that there are very general principles that are very widely shared across human cultures, as long as one does not insist that they generate absolute prohibitions.

According to al-Jabbar, we need to distinguish rational worship and religious worship. Both kinds involve obligations that are assigned by God. This seems to imply that we can worship rationally by obedience to the principles that are necessarily known, even if we do not know about God, and even if the obedience is not consciously directed towards God. On this view, it is only in relation to religious worship that God must be “described with every and each action,” to use al-Maturidi’s terms.