In none of these usages does the term persona have the connotation of emotional individuality or unique consciousness that clearly belongs to the term in contemporary usage. It is quite certain that the trinitarian use of persona does not point to three wills, three emotionally unique beings, or, as several eighteenth-century authors influenced by Cartesianism argued, three centers of consciousness; such implication would be tritheistic. It is equally certain that contemporary theological statements to the effect that the God of the Bible is a “personal” God point not to the Trinity, but to the oneness of the divine will in loving relation to creatures. In other words, despite the variety of usages and implications we have noted, the patristic, medieval, Reformation, and Protestant scholastic definitions of the term persona are united in their distinction from colloquial modern usage. In brief, the term has traditionally indicated an objective and distinct mode or manner of being, a subsistence or subsistent individual, not necessarily substantially separate from like personae. Thus, in trinitarian usage, three personae subsist in the divine substantia or essentia (q.v.) without division and, in christological usage, one persona two distinct naturae, the divine and the human. This can be said while nonetheless arguing one will in God and two in Christ- since will belongs properly to the essence of God and to the natures in Christ, and in neither case to persona as such. Thus, in the language of the scholastics, persona indicates primarily an individuum (q.v.), and individual thing, or a suppositum (q.v.), a self-subsistent thing, and more specifically still, an intelligent self-subsistent thing.
~Dictionary of Latin and Greek Theological Terms, p 226-227