There are two interpretations of the advice given his father in Dylan Thomas's poem, "Do Not Go Gentle into That Good Night":
- The poet exhorts his father to "rage against the dying of the light" because it will demonstrate to his son that he does not wish to leave the living.
- The poet wants his father to show fierce tears of rage against "the dying of the light" because of the futility of human activism and freedom.
The first interpretation can be substantiated with the exhortations of the son to affirm life to the end, rather than leaving life meekly with a complaisant acceptance of death:
Old age should burn and rave at close of day [implied metaphor for death],
Rage, rage against the dying of the light [implied metaphor for life].
The second interpretation can be extracted as the speaker alludes to the futile efforts of wise men, good men, wild men, and "grave," or serious thinkers and philosophical men, that are mentioned in the second lines of each tercet; these valuable men's insights have been ignored by the rest of humanity. The men of wisdom should display fierce tears of rage against "the dying of the night"; that is, the end of their wisdom as death comes to them and human minds remain darkly closed [the implied closed minds = the metaphorical "night] to the insights of these individuals. Likewise, the father, too, should "rage" against the futility of the human condition.