1. But make no mistake about it: those prophetic visions weren’t what we’d term “figments of the imagination” or any sort of curious visual ruminations, and they certainly weren’t hallucinations! Prophets weren’t shamans, wizards, or what’s termed “intuitives”: they were especially righteous, gifted, holy and specifically-chosen rare individuals who were trained by elder prophets when the prophets were young, and were granted manifestly G-d-given skills (see Hilchot Yesodei Ha-Torah Ch. 7).
As such, they knew very well that they were seeing “fresh manifestations” of “G-d’s Glory” that was “brought about just for them”, as Ramchal put it, that would enable them to “comprehend a revelation of G-d’s presence”. That is, they knew their visions were granted by G-d Himself of His own intentions and concerns, and they never doubted its veracity.
2. Ramchal then offers a very home-spun analogy so that we might understand their revelations and how convinced they were of its authenticity. We’re asked to imagine “seeing your friend through a glass window” — someone you know well. Even though “your friend himself would be behind a glass” and you wouldn’t be seeing him straight-on, “you’d nonetheless be certain that you’d be seeing that friend” since you wouldn’t confuse him for anyone else.
And in fact, “even if you were to imagine that the glass were to be transformed somehow”, that is, even if it was somehow misshapen or colored-over, “so that your friend behind it would appear different than he was” as a result — still and all, “you’d undoubtedly know that it was your friend himself whom you were looking at” behind the glass, since you were so familiar with him. And you’d quickly realize that while his image was being affected by the glass, he was still himself.
So, too, when a prophet would see an image of G-d before his eyes, Ramchal concludes, he would know for certain that it was G-d Himself hidden behind that image, since G-d was so familiar to the prophet. And even though He would appear behind a “glass” — an impediment in the form of an inner, and striking image that G-d had formed within him — the prophet would know that it would still be Him right there and then.
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.