Malbim: The fourth matter is secrets and hidden matters of Torah. Some attain them via the power of Binah. From his Binah he understands Hashem's grandeur, His deeds and wonders in Ma'ase Bereishis, and His legions and camps in Ma'ase Merkavah. Some attain them via Da'as. They are clear Yedi'os in the Nefesh of Kedoshim with clear hearts in matters of Elokus. A prerequisite for Da'as is straightness - the shortest line between two points. Da'as applies to all that man knows via his senses or axioms. He must coordinate scientific knowledge in the shortest way to know it. This is very hard for man. Usually he goes in roundabout paths, and tests until he reaches clear knowledge. However, clear knowledge of secrets of Torah are straight for those who find Da'as, They find Da'as Elokim in their Nefashos, via the Torah and Divine help in a straight, short way. Reasoning and comparisons of Tevunah arouse many possibilities; he must reject the false ones. However, secrets of Torah, they are all clear to a Chacham who understands by himself. He attains Hashem's honor, grandeur and deeds without any tilting away from the point of truth.