Because the purpose of The Metaphysical Demonstration of the Existence of God is to treat solely of what can be known by reason without the aid of revelation, Suárez addresses theological issues only when necessary to further explain a particular philosophical point. Nevertheless, there are a number of issues raised by Disputations 28 and 29 that are of general interest for their influence on Christian principles and issues.
The most obvious issue of interest to modern Christians is the possibility of a philosophical proof for the existence of God. Whether such a proof is even possible is still hotly contested and has been a source of continual debate among philosophers and theologians throughout modern times. The possibility of a proof still continued to receive considerable support through the time of Descartes, but such support has waned considerably since the criticisms leveled by David Hume and Immanuel Kant. Working within the tradition of negative theology, which emphasizes the incomprehensibility of God, some contemporary theologians and philosophers have questioned whether it is even appropriate to attempt to know God on a purely philosophical level.
Of a more theological nature, however, Disputations 28 and 29 contain interesting discussions of aspects of the doctrine of the Trinity (that God is three persons, but one god), of the nature of God’s free will, and of how, in accordance with principles of logic, it would appear that there must have been a first man. For instance, the question about the Trinity is how the primary division of being into infinite and finite is possible because either each person in the Trinity is finite (which is impossible for divinity) or infinite (which means that infinity is multiplied). Suárez, however, concludes that there is no difficulty because the three persons share in the same divine essence—thus, they are not finite, but neither is infinity multiplied.