WE GET LETTERS: Gary (Amygdala) Farber catches me in an apparent misrecollection:

Er, actually, Clarke had the monolith give Moonwatcher the idea of tool-using. That's the point of the jump-cut to the space ship: from one tool to another, a big leap on our scale, but a small leap on the Alien scale, including as measured by their quasi-tool, the monolith. If you doubt this, I refer you to the books "Lost Worlds of 2001" written by Clarke himself, and to Jerome Agel's book on the making of 2001.

I don't doubt it at all. It's been a very, very long time since I read the original Clarke novel. But in my feeble defense, I only referred to the novel (in the piece below) as a convenience, so that I could refer to the Thinking Hominid by name. For the purposes of my larger observation, I was describing the scene, not from the novel but from the Kubrick film -- and, insasmuch as the scene, as filmed, contained no clarifying dialogue or omnicient narration, the viewer is free to infer whatever they like. Such are the perils of ambiguous artistry.

In fact, regardless of the filmmakers' intent, I can make a strong case for my interpretation of events, because it resonates so clearly in the last half of the second act, with Dave Bowman taking the place of the Thinker, and HAL becoming the Corrupted Feeler. I would put it to you that, if you could read Dave's thoughts while he wordlessly performs that microprocessor-ectomy on HAL, they'd be along these lines:

HAL, you have demonstrated by your prior actions that you are dangerous, you are unpredictable, you cannot be trusted -- and I cannot negotiate with you in good faith. So, for the sake of my own survival, and so that my people may continue to evolve! -- and as much as it pains me to make this terrible choice -- I have no choice but to kill you before you kill me.