In defining the qualities of Modernism, Virginia Woolf writes of a shift that takes place within human consciousness. This sense of change is an essential part of the Modernist movement: "All human relations shifted... and when human relations change there is at the same time a change in religion, conduct, politics, and literature.” With this understanding, The End of the Affair can be seen as Modernist. One way is in how Bendrix's understanding of consciousness is "shifted." Bendrix has to experience the shift from a specific romantic type of love to a wider construction that encompasses the divine. Bendrix's sense of shift and change is a part of the shift that takes place within his characterization. This is one way in which Bendrix embraces a sense of Modernism in his change.
I think that another way in which Modernism is evident can be seen in the relationship itself. The ending of the affair is an abrupt one, something that Bendrix fails to see as possessing any rational understanding. Even though he comes to the realization that Sarah ended it as a sacrifice for something larger, Bendrix fails to understand the rational calculus for the affair ending. In addition to this, Bendrix's own irrationally jealousy toward Sarah undermined any real and sustaining love between both. This represents Modernist tendencies in its assertion that rationality is absent, reflective of another "shift" in consciousness and being in the world.