How can it be that "Knowledge is a light that God casts into the heart of whomever He wills"?

The manner in which Allah casts knowledge into hearts is unknown to us; it is an act of Allah, of which we only comprehend what He has informed us. Allah Almighty said: "O you who have believed, if you fear Allah, He will grant you a criterion." So, Allah casts the light of knowledge into the hearts of the pious. The closer the heart is to Allah, the more the evil influences depart from it, and the stronger becomes its light of discerning the truth. Indeed, knowledge is a light that Allah casts into the heart, by which the servant distinguishes between right and wrong. Malik said to Al-Shafi'i: "I see that Allah has cast a light upon your heart, so do not extinguish it with the darkness of disobedience."