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The flaws in logic lie in demonstration and definition.

As for “demonstration,” its logical form is valid, and when its premises are sound, it undoubtedly yields sound knowledge. The error, however, lies in two things:

First: There is absolutely no evidence for restricting its premises to the categories they have mentioned. They are correct in what they affirm, but not in what they deny. On what grounds can one judge that certainty can arise only from these particular sources? If someone bases this on what he finds within himself, how can he know that the rest of humanity—even the prophets and the friends of Allah—cannot attain certainty by other means? Indeed, reality shows otherwise.

Second: This demonstration does yield knowledge. But how is it known that no human heart can acquire knowledge except through demonstration of the kind described? We have, in fact, seen many things that some people know immediately or through sense perception, while others know them through reflection and syllogistic reasoning. Thus, they denied what they did not fully comprehend: knowledge acquired through premises outside these restricted categories, or without any analogical or syllogistic reasoning at all. Indeed, the most accomplished of their later thinkers claimed that the knowledge of the prophets and the friends of Allah can be acquired only