1. “Prophecy”, Ramchal declares, “is the knowledge and comprehension of G-d’s Glory that He grants prophets”, i.e., it is the clearest and deepest understanding of G-d’s ways in the world that a human being could ever hope to achieve .
But let’s make it clear that prophecy grants one a profound understanding of G-d’s interactions with the world, to be sure — but not an understanding of His very being, as that’s simply unfathomable to even the greatest of prophets.
In a way we’re being told that while the prophets were privy to G-d’s actions, mechanisms, demands, preferences, and expectations; to His displays of satisfaction or dissatisfaction which is to say, to His manifestations of mercy, judgments, and of life, well-being, as well as all the other traits attributed to Him — still and all no prophets were privy to G-d’s “heart”, if you will, or to His private “ruminations”, which are out of bounds. In other words, they could “see” Him at “work” if you will, but never at “home”.
2. That’s not to deny that they could actually envision G-d’s complex and variegated influences upon the world and the principles upon which they’re based, for they could. And it’s also not meant to deny the fact that they could grasp the past, along with all of its implications, as well as the future with all its promises based on that. They could grasp all that, too.
After all, they were acutely aware of all the forces at play all along, and by thus focusing upon them they could ken how those forces played themselves out in the course of time, broadly and deeply, within and without. Thus their reach was vast and profound, and was grounded in G-d’s intentions for the universe. But He Himself was beyond their ken.
 For kabbalistic references to this and the next few chapters see Klallim Rishonim 36.
Rabbi Yaakov Feldman has translated and commented upon “The Gates of Repentance”, “The Path of the Just”, and “The Duties of the Heart” (Jason Aronson Publishers). His works are available in bookstores and in various locations on the Web.