Larkin's poem is about the "toads," as he calls them, of work and responsibility. The external toad sits on him from the outside, forcing him to work six days a week so that he can—maybe—pay a few bills. This "toad" represents the way society is set up: the vast majority of us have to toil at a job we aren't too crazy about to get the money to live. It's a social expectation that we work. It's what we go to school and train for.

But as Larkin's speaker points out, some people get away from this external "toad" of social expectation by living by their "wits." These are the trickster types in society that the speaker describes in denigrating terms. Another class of people who don't have to go to work every day are the poor who live on the dole and patch together a life. They are often thin, can't take proper care of their children, and may have to warm themselves by lighting fires in "buckets," but somehow they barely get by.

Yet, the speaker says, it is not only external pressure from the outward "toad" of society that keeps the speaker drudging away at work: there is also some internalized "toad" that tells him he must adhere to this round of duty and work. It is the double whammy of society's "toad" and his own internal soul "toad" that keeps his nose to the grindstone.