A thing is not fully apprehended merely by stating its formal limit. One who has no prior knowledge of it can only come to know it once he has been acquainted with something that resembles it, even in a single respect; then, from the doubtful and shared attributes it holds in common with other things, one composes a description that singles out the object in question.
Whoever reflects on this will grasp its reality and will see how human beings come to know the unseen matters they have been told about—the angels, the Last Day, and the varieties of bliss and torment in Paradise and Hell. He will also recognise how this bears on their knowledge of God Most High and His attributes, and why many of the early Muslims said that the mutashabih refers to promises and threats, whereas the muhkam refers to commands and prohibitions. He will understand why it is said that the Qur’an is acted upon in its muhkamat and believed in its mutashabihat, and that the taʾwīl of the mutashabih—that is, knowledge of the manner in which the reported realities truly are—is known only to Allah. As for its taʾwīl in the sense of explanation and intended meaning, this is known to those firmly grounded in knowledge, as we have detailed elsewhere.
All of this applies when the one who asks, “What is it?” is ignorant of what the name denotes. If, however, he already knows the named entity and how the name points to it, he requires neither a distinction between it and other things nor an explanation of the name’s denotation. What he seeks is something beyond mere differentiation, and this—according to the logicians—is what is sought by someone asking for the definiendum; the answer, in their view, is what is given in reply to the question, “What is it?”
What such an inquirer may want could be the mention of hidden properties previously unknown, the exposition of its efficient or final cause, the identification of the constituents out of which it is composed, or the knowledge of its very reality—something the respondent may not know, or may know yet lack words to convey, as in the case of someone who asks about the essence of the soul and the like.