Dylan Thomas's aim in Under Milk Wood is to change people's perceptions and to treat trivial imaginings as life-enriching experiences. The story will "Begin at the beginning..." and each character or "voice" will make a valuable contribution to the overall effect of the play. The play is most certainly set in Wales but Thomas is able to give his voices a universally-appealing familiarity. Thomas wants to ensure that everyone listening, reading or watching the play can relate to the voices in it without becoming too involved in unimportant details.
A main theme is the passage of time and also the circle of life as, "Tick tock tick, tock tick tock..." we are reminded that "Time passes. Listen. Time passes." The fact that "Babies and old men are cleaned and put into their prams" signifies how enduring life is. No matter who a person is, or where he may be from, he can identify with this inescapable fact. Therefore, death and life—both of which revolve, in a Christian community, around religion—support and continue the time theme. Having been "born to die," as Reverend Eli Jenkins points out, should be enough to keep people grounded.
Irony is used to further reinforce these interconnected themes of time, life, death and religion. Life is full of irony and it is not lost on the reader who recognizes the complexity of life in the form of Captain Cat, who "sees in the dark" and yet is blind. There is also the relationship between Mog Edwards and Myfanwy Price and the contradictory "I love you until Death do us part and then we shall be together for ever." The fact that it is life that stands in their way is significant.
Much of Dylan Thomas's work has been criticized for its complexity but the simplicity of the voices in Under Milk Wood is a purposeful attempt by Thomas to stop people from overcomplicating their lives and then missing out on all the intricacies that complete a person.
Dylan Thomas was in poor health during World War II and was therefore in a category of men who would most likely not be called up for active duty. This was acceptable to him as registering as a conscientious objector was not feasible for him. He then participated in film-making during WW II for Britain's Ministry of Information mainly due to his debt. This participation is said to have influenced some of his future works. The exposure certainly made him more aware of the political agenda of some of his contemporaries.