Despite Open Theism's claims for a robust 'Social' Trinitarianism, there exists significant inconsistencies in how it is portrayed and subsequently applied within its wider theology. This sympathetic, yet critical, evaluation arises from the Pneumatological lacuna which exists not only in the conception of God as Trinity, but the subsequent treatment of divine providence, soteriology and eschatology. In overcoming this significant lacuna, the thesis adopts Francis Clooney's comparative methodology as a means of initiating a comparative dialogue with Pentecostalism, to glean important insights concerning its Pneumatology. By engaging in the comparative dialogue between to the two communities, the novel insights regarding the Spirit are then incorporated into a provisional and experimental model of Open Theism entitled Realizing Eschatology. This understanding of Open Theism emphasizes the Holy Spirit's ongoing work within a broader Trinitarian framework and suggests how the co-creation of reality between God and humanity possesses a significant Pneumatological component.