Thus, the incidental causes of error in the inward or outward senses and in reason are like illnesses that affect the activity of the body and soul: soundness is the normal state, both in perception and in activity. For Allah created His servants with an innate disposition. Errors in these matters are recognized through their particular causes, such as yellow bile affecting taste, misalignment of the eyes, and similar conditions. Otherwise, anyone who examines his own firm convictions will find that most people who are certain of things that do not warrant certainty derive their conviction from some form of desire. As Allah Most High says:

“Indeed, many lead others astray through their desires without knowledge.”

And He says:

“And who is more astray than one who follows his desire without guidance from Allah?”

This is why you find the Jews standing firmly by and persisting in their falsehood, because of the arrogance, envy, hardness of heart, and other desires within them. As for the Christians, they are more deeply misguided, although they are generally less evil in their habits and character. Yet they are not certain of most of their misguided beliefs. Rather, upon examination, you find that anyone from either group who abandons desire and gives the matter some consideration comes to recognize that Islam is true.

The point here is that a person’s awareness of whether he knows or does not know rests on his finding within himself that he knows. Thus, against someone who denies knowledge, we offer no argument other than that we find within ourselves that we know. Likewise, scholars argued against those who deny mass-transmitted reports by saying that we find within ourselves that we know these things and are certain of them, just as we know and are certain of what we have perceived through our senses.

Scholars who have examined the matter rigorously have made the attainment of knowledge through a report the criterion for establishing mass transmission. They did not delimit it by any number or characteristic; rather, whenever knowledge is attained, that is what counts. A person finds within himself that he knows, and this is true.