[Note some of this is a further development of the post about Descartes’ rational presuppositionalism. You can find that post here. This series will move on to explore a similar version of presuppositionalism as it is found in the theoretical thought of Baruch Spinoza.]

One of the human race’s great metaphysical questions is whether or not God exists. This question divides many authors in the Western intellectual tradition. Some think that God does not exist. Nietzsche, Hobbes, and Hume, for example, fall into this category, while others such as Plato, Aristotle, Augustine, Aquinas, Descartes, and Spinoza think that a god or the Christian God does exist. Among those who believe that God exists, there is a division between them about how to correctly reason or argue for the existence of God. On one side, Descartes and Spinoza think that God should rationally be assumed or presupposed in any argument for God’s existence. Others, such as Aristotle, Augustine, and Aquinas think that arguing from the nature of existence, or being itself, is the best way to make a case for God’s existence. The difference between these two groups is one of methodology. Descartes’s and Spinoza’s position can be called rational presuppositionalism, while thinkers such as Aristotle, Augustine, and Aquinas hold the position known as natural theology (or natural philosophical theology). The next couple of posts will critically explore the philosophical differences between the approach of Descartes and Spinoza (rational presuppositionalism) and the natural theology of Augustine and Aquinas.

The concept of natural theology will be developed further in the upcoming posts. However, in brief, natural theology is a philosophical and theological way of reasoning to the existence of God which starts with the reality of being and becoming, or the fact of reality as it is, and uses the natural laws of logic, which are properties of being, including the principle of causality to conclude that God exists necessarily, eternally, and transcendently. Both Augustine and Aquinas utilize this general form of natural theology. Presuppositional rationalism, on the other hand, is the position that God’s existence must be presupposed and reasons from that point. With presuppositional rationalism—primarily in regards to Descartes’s and Spinoza’s position—God is presupposed because God is conceived as a “Perfect Being” and existence necessarily applies to a Perfect Being. It is also a form of rationalism because it holds that all genuine knowledge comes from rational thought apart from sense experience, or any appeal to concrete reality or Being. In this context, Spinoza puts forward three ideas worthy of careful reflection. They are his philosophical presupposition that God exists (that is, God must be presupposed in any argument about God’s existence), pantheism (God and the universe are the same thing), and his conception that the universe is the cause of itself (self-creation or self-causation).

Spinoza’s description of God is helpful at this point. In rational geometric fashion, Spinoza presents definitions and axioms which he uses to explain his conception of God. He defines God as “Being”—not the transcendent cause of Being—but an imminent Being with infinite substance, “By God, I understand Being absolutely infinite, that is to say, substance consisting of infinite attributes, each one of which expresses eternal and infinite essence” (589). God, as a kind of substance, is “that which is in itself and conceived through itself,” (591), and is the “cause of itself” (590). For Spinoza, God and natural substance are one. God is a self-caused substance.

In many ways, Spinoza follows Descartes’s presuppositional rational methodology, so it is helpful to briefly understand Descartes’s line of reasoning. Both Descartes and Spinoza believe that God exists because God is a “Perfect Being.” Perfection must be a property of existence and because God is thought, or conceived to be, perfect, God necessarily exists. This is a form of thinking which argues that if God is the greatest being that can be conceived, God necessarily exists because existence is a property of Being (what is called the ontological argument for God’s existence). Both Spinoza and Descartes hold to this conceptual scheme of God’s existence. Descartes explicitly connects his presuppositional approach with God as a “Perfect Being.” When trying to overcome the question of how to prove external reality or whether or not one can trust their thoughts, Descartes offers this line of reasoning,

And though the wisest minds may study the matter as much as they will, I do not believe that they will be able to give any sufficient reason for removing this doubt, unless they presuppose the existence of God. For to begin with, that which I have just taken as a rule that is to say, that all the things that we very clearly and very distinctly conceive of are true, is certain only because God is or exists and that He is a Perfect Being, and that all that is in us issues from Him. (277, emphasis added)

Notice what Descartes says here—one must presuppose God exists because God is a Perfect Being which must include existence. God exists because existence is a property of Being, and in order to be the most Perfect Being, such a Being must have the property of existence. Descartes calls this a “metaphysical certainty” (277). When thinking of God, according to presuppositional rationalism, one is simply presupposing God’s existence. In other words, according to this Cartesian approach, God is the perfect Being which must be assumed when arguing for the existence of God. The presuppositional character of Descartes’s argument further reasons that if our thoughts and things we conceive of are true, they are true because God exists.

Next time, we will go into the presuppositional method of Spinoza as he follows much, though not all, of Descartes’ approach. Finally, it is worth noting that presuppositional rational reasoning is not new and does not begin with Van Til, Bahnsen, or Frame. In fact, presuppositional thinking does have significant similarities to the approach of Descartes’, Kant, and Spinoza and includes the usual errors.

Works Cited

Descartes. Bacon, Descartes, Spinoza. Great Books of the Western World. Vol. 28. Encyclopedia Britannica, Inc., 1999.