You're free to speculate as you wish about the philosophical and allegorical meaning of the film—and such speculation is one indication that it has succeeded in gripping the audience at a deep level—but I don't want to spell out a verbal road map for 2001 that every viewer will feel obligated to pursue or else fear he's missed the point.
- Stanley Kubrick on 2001: A Space Odyssey 
Few films have inspired as many interpretations and explanations as 2001: A Space Odyssey. An abundance of formal and amateur cogitation exists on the film, strictly engaging the structural and allegorical elements of the film, such as the aspect of evolution. Here I hope to address for the first time its philosophy.
The use of words in 2001: A Space Odyssey, one of the film’s most radical innovations, will be the starting point for our discussion. We begin in the “Dawn of Man” era with pre-vocal visual cues and bestial grunting. Then we leap ahead to the discovery of a monolith on the moon and what do we get, philosophical exegeses on the nature of the monolith, hordes of ecstatic scientists, desperate philosophical reasoning by the crew about god and existence? No. We get a phone call home, cautious questioning and small talk between scientists, and Dr. Floyd’s generically bureaucratic speech (which, he’s later told, “beefed up morale a hell of a lot.”) The most impassioned dialogue is HAL’s as he negotiates for his “life.” The last chapter is of course without dialogue and we get no epistemological or ontological discourse or verbal coda of any kind.
Such banalities of life indeed stand out painfully: Dr. Floyd’s over-acted phone call home to his daughter and the phony applause he gets before he speaks. Worse, the “victory” photo of the scientists in front of the moon monolith, reminiscent of hunters in front of their kill or sportsman in front of their trophy, is painfully more ironic by the high-pitched music ramping up the tension as they pose (the prosaic “move together” hand gesture of the cameraman is the final blow). Also, the choosing of sandwiches, Dr. Poole’s (“Frank”) “Happy Birthday” phone call from his parents (and their small talk during the call), and the eating of the “space/TV dinners” whilst actually watching television. The irony of the latter situation is that you might think seeing themselves on TV might engender some kind of response.
The instinctive interpretation of these uncharacteristic and jarring manipulations of dialogue is that this usage is an attempt to draw attention to some unsaid ideas. While this is essentially true I believe it doubly belies the purpose of the dialogue. It’s not so much that the unsaid is more important, but that saying is not even a viable means of expression for what Kubrick intends. Nietzsche said it best, “Thus Thales had seen the unity of all that is, but when he went to communicate it, he found himself talking about water!” 
The greater significance, though, lies in the problematic fact that dialogue is inherently explanatory. By offering up internal ideas and qualifications about the monolith, for example, Kubrick would delimit, sway, and ultimately corrupt the interpretation of the viewer. Without explicative dialogue the viewer does not have to tangle with fabricated internal opinions; the viewer’s opinions become the only ones.
We must first remark, though, on the peculiarity of film. Mainly, that within the film the director is privileged absolutely to ascribe meaning and to define any and all. He can identify what a thing is, noumenally. Let us now say the monolith exists in itself, i.e., noumenally and non-metaphorically. All we get from Kubrick is, however, the phenomenal, i.e. what something appears to be to us. Internally, there is no explication of the monolith: the individual “understandings” of the humans are not disclosed and no narration is provided. We can make no assumptions of it based on internal evidence. Our “understandings” of it, on account of the lack of contradicting internal evidence, are all that exist. They are metaphors we create in an attempt to explain. This is an almost Nietzschean perspectivism. We do not know what the monolith is and anything we could say is essentially a guess. The film suggests the noumenal is beyond understanding. In refusing to offer us “facts” Kubrick allows the film itself to act as the question, “What is knowing?”
Perhaps the ultimate irony is that we have this “Science Fiction” film that is thoroughly non-scientific. As Nietzsche said, “Science rushes headlong, without selectivity, without ‘taste,’ at whatever is knowable, in the blind desire to know all at any cost. Philosophical thinking, on the other hand, is ever on the scent of those things which are most worth knowing, the great and the important insights.” The film now becomes a metaphor, one for our human desire for such valuable insights. It is an attempt to understand our attempts to know by examining the nature of knowledge.
Kubrick has uprooted objectivism and left us only our metaphors, that is to say, our art, and our selves. The loose narrative of the film offers one comment, though, namely that our metaphors are enough. The monolith, now a symbol of the unknowable and not simply the unknown, appears at pivotal times in our history. Whether it occurs as a reminder that we humans do not and cannot know all is not pertinent, and while it does not necessarily spur us on, it definitely has not stopped our evolution. Our individual metaphors elevate us in spite of the elusiveness of the noumenal. The final shot, the Star Child, is our apotheosis.
 Norden, Eric. Interview: Stanley Kubrick. Playboy (September 1968). Reprinted in: Phillips, Gene D. (Editor). Stanley Kubrick: Interviews. University Press of Mississippi, 2001. ISBN 1-57806-297-7 pp. 47-48
Nietzsche, Friedrich. Philosophy in the Tragic Age of the Greeks. Gateway Editions. 1996