2001: A Space Odyssey ~ Extract from the Screenplay

obelisk / mushroom

Ape first apprehends Obelisk

...there are no natural objects to which Moonwatcher can compare this apparition. Though he is wisely cautious of most new things, he does not hesitate to walk up to it. As nothing happens, he puts out his hand, and feels a warm, hard surface. After several minutes of intense thought, he arrives at a brilliant explanation. It is a rock, of course, and it must have grown during the night. There are many plants that do this - white, pulpy things shaped like pebbles that seem to shoot up in the hours of darkness. It is true that they are small and round, whereas this is large and square; but greater and later philosophers than Moonwatcher would be prepared to overlook equally striking exceptions to their laws. This really superb piece of abstract thinking leads Moonwatcher to a deduction, which he immediately puts to the test. The white, round pebble-plants are very tasty (though there were a few that made one violently sick); perhaps this square one...?

- Extract from: Text of screenplay by Stanley Kubrick and Arthur C Clarke.