and His Messenger have deemed deserving of loyalty or enmity.*) (1) What is lawful is what Allah and His Messenger have made lawful; what is forbidden is what Allah and His Messenger have forbidden; and the religion is what Allah and His Messenger have prescribed. All these questions, therefore, are established by the revealed law.

As for matters that reason can apprehend independently, these include matters of nature, such as the fact that a particular medicine benefits a particular illness. Such a matter is known (2) through experience, analogy, and reliance upon physicians who learned it through analogy or experience. Likewise, questions of arithmetic, geometry, and the like are among the things (3) known by reason. The same applies to the question of the indivisible atom, whether bodies are alike or different, and whether accidents can or cannot persist. These and similar matters are known by reason.

This being so, whether a man is a believer or an unbeliever, upright or sinful, is a question of revealed law, not a rational question. How, then, can someone who contradicts what the Messenger brought not be an unbeliever, while someone who contradicts what another person claims to know through his reason is deemed an unbeliever? Does anyone become an unbeliever by erring in questions of arithmetic, medicine, or the subtleties of speculative theology?

If it is said:

‘They do not declare everyone who disagrees over a rational question to be an unbeliever. Rather, they declare an unbeliever anyone who contradicts the rational questions through which the truthfulness of the Messenger is known, for knowledge of the Messenger’s truthfulness is founded upon them (4): [upon certain specific questions] (5). If he errs concerning them, he will have no knowledge of the Messenger’s truthfulness and will therefore be an unbeliever.’