The Eye: what was it?

[Ibrîniðilpathânezel]

Hmm, Jackson's representation of the Eye always made me think that someone had left on the Flaming Eye Beacon atop Castle Anthrax....

Jackson's interpretation aside, the Eye was a symbol, but not Sauron's physical form in the Third Age. In speaking of Aragorn's confrontation with Sauron via the palantir, in letter 246, Tolkien says:

...in a tale which allows the incarnation of great spirits in a physical and destructible form their power must be far greater when actually physically present. Sauron should be thought of as very terrible. The form that he took was that of a man of more than human stature, but not gigantic.

So it would appear that Tolkien intended Sauron to have a physical man-like form in the Third Age. "The Eye" to me always equated with Sauron's attention, or his focused powers of mind. The stab of red fire mentioned in skip's original quote is to me no more of a surprise than the stab of white fire that came from Gandalf's upraised hand during the rescue of Faramir; the light is a manifestation of power being exerted, and Sauron was certainly exerting his power to see all he could of his enemies' actions during the battle before the gates. He was probably exerting considerable power to control his armies from afar as well. I could well imagine that his "very terrible" physical form might have hideous and piercing eyes, which his minions and slaves would remember quite well, and come to equate with him.