There are two characters in "Do Not Go Gentle into That Good Night" by Dylan Thomas, the speaker and the dying man. The speaker is the son and the dying man is his father ("And you, my father, there on that sad height"). The speaker makes reference to four kinds of men, one in each of the four interior stanzas of the six stanza iambic pentameter poem in a repeating aba aba rhyme scheme, varied in the last stanza with abaa.
The four kinds of men, who are not characters in (meaning actors in) the poem are (1) "wise men," (2) "Good men," (3) "Wild men," and (4) "Grave men." The speaker tells how each has an epiphany of truth or error, such as "Good men" who realize "how bright" their good deeds "might have danced" somewhere other than where they were ("in a green bay") or the "Grave men" who realize they might have been equally grave ("meteors" suggests grave in astronomical research) and yet been happy ("gay"). Yet these men do not participate at all in the brief narrative of the poem and so cannot be described as characters.
The speaker maybe described as ardent, perhaps even desperate; intelligent; philosophical; impassioned; and deeply devoted in love to his dying father. The ardent fervor of his verse, especially the repeated end lines, "Rage, rage, against the dying of the light" and "Do not go gentle into that good night," which itself is a repetition of the opening line, show he is desperate in making his impassioned appeal for his father to fight off the last closing light of life, to hold strongly to the light of life as ferociously as might be, despite his failures and inadequacies, similar though they may be to the four men's.
He can be described as intelligent and philosophical because of his examples of the four kinds of men, who are used with great effect. They make his point that despite the "frail deeds" that "forked no lightning" and the songs "for the sun in flight" that were but grief for "it on its way" and the "Blind eyes [that] could blaze like meteors and be gay," his dying father should not yield to giving up the "rage against” death and should “not go gentle into that" dark night of death--a night that Thomas ironically and stoically styles as a "good night."
The father is a passive character and as such can only be described as a reflection of what the son says. It seems from the son's words that the father has yielded to the weight of his failures and loses and is quietly awaiting his expected sorrowful end. It would seem from the example of the four kinds of men that the father has in some ways been a disappointment to himself and is thus judging himself at the end of his life and passing a verdict against himself that it is best that he leave the light of the "sun in flight" and pass "gentle into that good night.” The speaker's deeply devoted love for his father can be seen in the earnestness with which he pleads with his father to recognize that his faults and failures are the same as others’ and to fight in "rage against the dying of the light."