The aim of this paper is to investigate the meaning of trust; specifically, it is an attempt to draw out the ontological and ethical meanings of trust. To this end, I shall use Niklas Luhmann’s and Anthony Giddens’s views of trust. Through considerations to their views, I present the meaning of trust as the maintenance of ontological security and emotional protection against existential anxiety. This ontological meaning of trust is related to the ethical meaning of trust. Trust has the character of a“gamble.”When I trust another person, I depend on his goodwill toward me. Trusting another person, then, reveals the ethical meaning of trust, in that the person trusted with discretionary power assumes a sense of responsibility for the person doing the trusting.