The Openness of Being explores natural theology and the foundational issues of what is and is not natural theology, along with some of the most important issues to bear in mind while exploring natural theology, such as the value of establishing a clear definition for key terms used in the argument. Mascall examines several arguments for the existence of God, referring to the strengths and weaknesses of each and referring to many published works on philosophy and theology. While the ontological argument is discussed and dismissed, the author develops the cosmological and metaphysical arguments further. He concludes that through these methods, if one comes to recognize a being as contingent then one must also recognize the existence of God. Furthermore, Mascall argues that, as the transcendent ground for all contingent being, several things can be known about God, including that God holds a relation with time but is timeless.