The question of the existence of God is one that is part and parcel of contemporary society’s general interest in religion. All religious traditions consider the issue of some divine being, even those which reject the existence of a divine figure precisely because their religious outlook is formed on the basis of the lack of a divinity. The three main Western monotheisms affirm the existence of a single divine being which is the cause of the existence of all things. Nevertheless, there are important differences amongst these monotheisms on how to conceive of the divine being.
Given the close association of belief in the existence of God with religious belief more generally, it is often assumed in non-specialist discussions that belief in the existence of God is an article of faith and thus held on the basis of faith. Hence, belief in God is often taken to be on the same level as faith in the doctrines derived from revealed scripture, so that if we can reject scripture we can reject the existence of God. But if we look at some representative thinkers of Western monotheism, we see that for them the existence of God is not something that one holds on the basis of faith, but that one can have a rigid demonstration of God’s existence on the basis of natural reason. Indeed, St Thomas Aquinas, a representative Catholic theologian, argues in Summa Theologiae, Ia, qu. 2, art. 2 that the existence of God is not an article of faith but a preamble to the other articles of faith. This is to say, one must believe in God before one has faith, and that one’s faith builds upon belief in God. Hence, belief in God is not a part of faith, but precedes faith, and so is not held by faith. So how does one come by this belief?
Before proceeding it will be useful to distinguish some terminology. Often the terms ‘belief’ and ‘faith’ are used interchangeably when in fact they are distinct. One can have all sorts of beliefs, and they can be justified either on the basis of reason or on the basis of faith. So I believe that the earth is spherical because I have read the justifications of that outlook and I have seen pictures of the earth from space; this is a belief which is justified by natural reason. I believe that the floor beneath me will not collapse all of a sudden, not because I have investigated the integrity of the building materials or its design, but because it has remained solid for a substantial period of time and I have no reason to think it will not hold good in the future. This is a belief held by faith, since a number of factors come together to bring about my assent to that belief without direct confirmation. So belief is a kind of mental content, and one can assent to a belief either on the basis of natural reason providing a proof or on the basis of faith. Notice here that faith is not the attitude of believing without thinking; since in the belief that the floor will not collapse beneath me, it is hardly the case that I believe it without thinking, because if challenged as to why I believe this I could go on to give various reasons. But crucially the reasons do not directly amount to proof and so do not command the assent that demonstration by natural reason commands.
Turning then to belief in God, I have noted that in Western monotheism it was not held to be something justified by faith, and indeed we have seen one representative thinker who held that it is a belief that must be in place prior to faith. We can go through a number of important thinkers who all offered demonstrations for the existence of a divine being, to name a view from various religious traditions: Plato, Aristotle, Plotinus, Augustine, Aquinas, Anselm, Scotus, Moses Maimonides, Avicenna (Ibn-Sina), Descartes, Leibniz, Kant, Plantinga, Lonergan. These figures cover diverse religious traditions: Pagan, Catholic, Protestant, Jewish, Islamic, and range from the ancient world to the twentieth century. Their demonstrations of God are well known and well documented in specialist circles and contemporary commentators on religious issues really ought to be familiar with their thinking if they are to comment on issues pertaining to the existence of God with any sort of authority (even if they wish to reject all such demonstrations of God’s existence).
But why have thinkers throughout the ages thought that the existence of God can be demonstrated and that it is not an article of faith like the Trinity or the Incarnation?
I think that what has impressed so many thinkers is the sheer existence of things; the fact that things are but may as well not have been has stimulated many to consider whether or not what accounts for the existence of things can be just another of those things which may as well not be. This observation has often led thinkers to progress on a form of complex reasoning by which they conclude that the very existence of things is not something explicable by appeal to any one thing whose existence is such that it may as well not have been, but must be located in something whose existence is such that it cannot not be, i.e. something that is simply pure existence itself and not an entity participating for now in existence. This insight into things is something I think is to be found in some form in the major representatives of Western monotheism and it is brought to perfection in the thought of St Thomas Aquinas (I defend the viability of one of his proofs in my book Aquinas’s Way to God: The Proof in De Ente et Essentia).
My point here is not to go into the depths of specialist philosophical reasoning (I have done that elsewhere); rather, I wish to highlight that the question of the existence of God is not simply one of personal faith and so to be side-lined to some private realm. The existence of God has some heavyweight reasoning behind it, and such reasoning is natural, that is to say, it makes no appeal to revelation or private experiences; it simply appeals to realities and concepts such as the existence of things, causality, causal relations etc that any rational person can understand. This then entails that not only ought the existence of God be taken more seriously in the public sphere and not dismissed as a private belief, but that those who wish to dismiss belief in the existence of God as something irrational will have to deal with the very rational and indeed reasonable argumentation of the thinkers mentioned above. At the very least this should generate a worthwhile public discussion wherein views can be exchanged and engaged with on the issue without theists being dismissed as irrational, backwards, idiotic, and without atheists being dismissed as irreligious, sinful, evil.