We believe we think with our brain, but I think with my feet. 
It is only there that I come up against something hard. 
Sometimes, I think with the muscles of my forehead when I bump into something. 
I have seen enough electro-encephalograms to know there is no shadow of a thought. 
-Jacques Lacan 
Sufficiently obscure to enrage Noam Chomsky, this was the answer Lacan proffered to the problem of thought at a conference at MIT. 
Chomsky decreed Lacan a madman. Richard Webster, who famously critiqued Freud as an unscientific fraud who merely perpetuated the Judeo-Christian legacy in a cryptic form,  hypothesized that Lacanian wisdom was akin to a diet of stones which his insanity caused him to believe to be food and to persuade others to eat. Webster states that Lacan’s rejection of God caused him to set himself up as a God saying that Lacan preyed upon the human propensity to be moved by mystery, particularly when bound up with points of sexual reference, rather than rational explanations. Could we say, as Webster seems to, that Lacan, unlike the Christ, falls prey to the devil in the desert? A diet of rocks, even when by some divine magic we are given the illusion of bread, is still a diet of rocks.

Transubstantion is precisely how one may avoid eating stones. The distinction between stones and bread is a properly ancient discussion, perhaps as old as philosophy itself. Even in his trenchant critique of the powerful factions of his time Christ would not stoop to accusing his opponents of giving stones to their children when asked for bread. The accusation of a stone-eating magician, then, is only in part a critique of insanity or devious showmanship. As, in fact, the construct of insanity (or the life of the mind more generally) in our time is partially accurate diagnosis and partially a hasty construct borne out of fear because all is not right and when we are reminded of this we would hastily exclude those reminders.
It is precisely these boundaries, these false constructions that carried a trace of fear and complacency, at which Lacan pushed.

Thus the criticisms of madman, charlatan, or intellectual magpie all reveal a partial truth, and yet at the same time hasten us towards an unnecessary confusion and caution us not to deliberate and search for wisdom, since our initial posture of failing to comprehend is undoubtedly the proper one.

Lorenzo Chiesa  in Subjectivity and Otherness, a brilliant examination of Lacan as a systematic thinker, notes that discussion around Lacan is all too often comprised of either a flat out rejection of Lacan as too obscure and stylistically inappropriate, or else a near hypnotic recitation of Lacan as a cultic figure, when in actual matter of fact Lacan may be considered a difficult but systematic thinker, whose unusual style forces his students to be unable to adopt a merely pedagogical approach to thought.

This is in keeping with a particular French tradition, though it finds common ground with Hegel and Marx among others, that is unsatisfied with the kind of reified position offered by a positivist approach to science, which as a matter of course does consider the universe to be comprised of stones (i.e. abstract facts) that are to be considered from the external god-like position of the scientific mind.

The ingestion of knowledge, then, is the only appropriate metaphor for a human species. And humans are much more like magpies than we are inclined to consider.