What is the central idea of lewis's speech? why might he have chosen to express this idea at a princeton graduation ceremony

Iwill give brainliest banquo. how goes the night, boy? fleance. the moon is down, i have not heard the clock. banquo. and she goes down at twelve. fleance: i take't, 'tis later, sir. banquo: hold, take my sword. there's husbandry in heaven, their candles are all out. take thee that too. a heavy summons lies like lead upon me, and yet i would not sleep: merciful powers, restrain in me the cursed thoughts that nature gives way to in repose! using context clues, what is the meaning of the word "candles" and what effect does that have on the play? the night is cloudy, so no one can really see what is happening. there are no stars, which could be considered candles in heaven, so heaven cannot see the sin happening on the earth below the moon is not illuminating the heavens, so everyone up there is asleep. the candles from the surrounding countryside are all out, so macbeth can carry out the murder