Impressing the father
This novel is an allegory about what it feels like to impress one's father. That dynamic is backwards; instead of supporting the son's desires for the son's own life, the father accidentally makes the son believe that unless he impresses the father, he will fail to receive the love that he depends on for his health and well-being. This is not a sustainable emotional point of view, so we see the novel fall through various stages or iterations as Peter becomes slightly new versions of himself, ultimately landing on anhedonia and ennui.
Employment and distress
The motif of poor employment is a defining feature of why Peter can never impress himself. He only pursues the passions he feels he should, but those endeavors lack the root of motivation, which is Peter's own desire or passion for those jobs. He doesn't care about his jobs at all, so he enters a cycle of trying to find the right job for himself, but only through manufacturing a neurotic motivation that verges on cognitive dissonance. He cannot find a good path forward because he is not yet able to face his emotional demons. He wants to be loved and accepted, but secretly, his self-esteem is that of someone who has no emotional support, but he clearly has an entire community who loves him and supports him.
Judaism and tradition
Another manifestation of this character's growth is his eventual rejection of Judaism. That is the patriarchal religion of his forefathers (literally) so to reject it is a firm statement about existentialism and meaning. If the oldest religious myths on the earth are abandoned for whatever reason, the person who is freed from that religion is suddenly condemned to that freedom. Without a solid foundation for hope, he must finally admit that he has never really felt very hopeful in the first place. The portrait is clearly one of existential awakening.
Peter's sexual success
One would think with a self-esteem as challenged and complex as Peter's, he might not have enough joie de vivre to attract an impressive mate. Nope. He succeeds fairly easily, because his hyper-awareness of expectations and his general denial of status quos is attractive to the right kind of woman. The person whom he finds himself in sexual relationship with is cheating on someone else, showing that both of them are compatible because they are ready to betray their commitment and duty to family in order to do what they want. Peter is just damaged enough to not care what anyone thinks, and the novel suggests that such abandonment is rooted in power which is sexually attractive.
Comedy as a symbol
The symbolism of cocaine takes the protagonist from the shameful and frustrating religion of his youth into a new religion. By abandoning religion and doing drugs, the hero shows that he has officially decided to do what gives him pleasure (with the unfortunate background being his poor mental health; one gets the sense that he is staving off hopelessness with pleasure). Comedy is a perfect culmination of these energies, because comedy is a symbol which points to the horror of life's true nature. Comedy is a way of making people face the truth, because instead of sorrowing, the pain of comedy makes people laugh.
