For the most part, Murdoch uses the side characters in The Sandcastle as exactly that. They are peripheral to the action. In developing the subject of how Demoyte and Bledyard are representatives of polar outlooks, I think that one has to examine the role of self in each. Demoyte is a self- affirming force. He sees himself as central to what is happening around him. Demoyte is aware of his own position as headmaster, confirmed by the portrait that brings Rain into view. At the same time, he does not see limitations around himself and his friend, William. He believes that William should pursue life with Rain, and affirms that William should seize the moment that is upon him. As he articulates the capacity of what can be be done, Demoyte operates as a force of centrality in the narrative.
The central force of the individual that Demoyte affirms is representative of both himself and his support of what William should do. Such a position places him as a polar opposite to Bledyard. Demoyte argues that William should not proceed with his relationship to Rain. He argues that Rain "is a child" and that William should "reflect carefully before proceeding further." Demoyte represents the force of restraint in suggesting that individual actions must be subservient to a larger order and wider configuration. Demoyte argues that the individual action is this vision, while Demoyte suggests that there is paradigm within which human action must operate. In this regard, he becomes a polar opposite to Demoyte in the advice that both give to William.