One of the major tensions in These Impossible Things is between the young Muslim protagonists and their respective boyfriends who don’t share their religion. At the beginning of the novel, Kees is dating Harry, and Malak is dating Jacob, both of whom are white British men. Each young woman keeps her partner a secret from her family because their British Muslim families will not approve of their dating non-Muslim men. Since Malak believes there is no future for her relationship with Jacob, they eventually decide to part ways, and this is a decision she later comes to regret, despite his avowed willingness to convert for her. Kees, however, decides to marry Harry, though he, as a devout Catholic, has no intention of converting to Islam. Harry’s religious devotion, though ostensibly a barrier to his relationship with Kees, is presented as a way in which the two of them can connect with one another. Throughout the novel, various characters address the ways in which Islam and Christianity are or are not similar, and the novel argues that religious devotion itself—irrespective of the religion—is unifying rather than divisive.

The younger characters in the novel, including Kees and Jenna, note the primary overlap between Islam and Christianity: Both religions advocate the worship of the same monotheistic God.