Answer:
Commitment
Explanation:
According to Robert Sternberg, there are three components of love: an intimacy component, a passion component and a decision/commitment component.
Intimacy is the feeling of closeness in a relationship, passion refers to physical attraction and commitment is each partners' decision to maintain this love.
Philip is away and he and his wife don't see each other every day, and there are periods of absolute silence between them. They don't know what they are doing when they are apart but they trust in one another, knowing the other person is waiting for them to reunite. It is commitment, meaning, even if the husband/wife are not together, they are still reunited in thoughts and no party does anything wrong to jeopardize their marriage.