Najeeb Awad aims at defending the personhood of the Holy Spirit by proposing answers to these questions: What is the Holy Spirit in relation to God? Is He a spirit-like presence of a monistic deity; is He merely a charismatic, supernatural power bestowed upon Jesus; or is He rather the third divine person in the Trinity, who is co-influential in and co-constitutive of the Godhead? The author re-examines the validity of both Western and Eastern trinitarian theologies and corrects their reduction of the Spirit either to a mere 'relationship' or 'mode of presence', or to a semi-subordinate hypostasis in a hierarchical divine Godhead that exists by virtue of the Father alone. He argues that viewing the Godhead as a 'reciprocal koinonia' offers a balanced attention to the Spirit's person and actions. He then shows that the claim of the Holy Spirit's particular personhood provides new dimensions for understanding God's unfathomable and mysterious personal being.