According to the vast majority of recent Trinitarian theologians, to believe in the Trinity is to believe that God is Love: it is to believe in three divine Persons Who know each other, love each other, and give themselves to each other. St. Thomas Aquinas is rarely invoked as a patron of such a social approach to the Trinity. Aquinas's Trinitarian theology, after all, revolves around the immanent processions of a Word and Love within the unity of the divine essence. Many have assumed that this "psychological analogy" is removed from-or even incompatible with-interpersonal knowledge, love, and self-giving. Some have concluded that Aquinas is therefore unable to accommodate a social Trinity. Others have argued that he is open to a social Trinity, but that his psychological categories need to be complemented by a more overtly social framework. This study, however, shows that these psychological categories themselves are shot through with interpersonal knowledge, love, and self-giving.More specifically, Aquinas's psychological analogy is often accused of emphasizing the unity of the divine essence at the expense of the distinction of the divine Persons. In fact, it emphasizes distinction just as basically as it emphasizes unity, and it ensures that the distinction between the divine Persons is a radical one. Similarly, it is criticized for being a matter of self-knowledge instead of interpersonal knowledge, self-love instead of interpersonal love, and self-regard instead of self-giving. In fact, it is a matter of self-knowledge as interpersonal knowledge, self-love as interpersonal love, and self-regard as self-giving: it ensures that there can be no self-knowledge or self-love in God that is not just as basically interpersonal knowledge, interpersonal love, and interpersonal self-giving. Aquinas's psychological analogy, then, does not shut down the possibility of interpersonal Trinity. Nor does it need to be complemented from the outside by an interpersonal Trinity. Instead, it contains within itself an intensely interpersonal Trinity.