After a million years of shining sanity they could hardly have understood what power was destroying them.
11 seconds sound clip from the Forbidden Planet (1956) movie soundboard.
You can hear this line at 01:28:08 in the Blu-ray version of the movie.
Quote context
[...]
- Their own subconscious hate and lust for destruction.
- The beast. The mindless primitive. Even the Krell must have evolved from that beginning.
- Yes, young man, all very convincing, but for one obvious fallacy.
- Your mind refuses to face the conclusion.
[...]