In previous episodes I have discussed a couple arguments for the existence of God: the argument for “the One” and the argument from eternal truths. Both are kinds of cosmological arguments, characteristic of the thought of Plotinus and Augustine respectively. The central notion of a cosmological argument is that everything depends on something else for its existence and nature, except for one thing that is the ultimate source for everything else, one thing that is absolutely independent and necessary. With this episode I’d like to talk about another kind of cosmological argument that attends to this same central notion but in a slightly different way. This is the argument from the principle of sufficient reason. This argument was given its classical form by the German mathematician Gottfried Wilhelm Leibniz (1646 – 1716). Leibniz was also the one to use the term sufficient reason to refer to the principle, though it had certainly been expressed by many people previously.

The principle of sufficient reason, often abbreviated as PSR, is that “everything must have a reason, cause, or ground” (Stanford Encyclopedia of Philosophy). Leibniz said in his Monadology:

“Our reasonings are grounded upon two great principles, that of contradiction, in virtue of which we judge false that which involves a contradiction, and true that which is opposed or contradictory to the false; And that of sufficient reason, in virtue of which we hold that there can be no fact real or existing, no statement true, unless there be a sufficient reason, why it should be so and not otherwise, although these reasons usually cannot be known by us.”

Leibniz expands on this, leading to an argument for God, in a passage worth quoting extensively:

“In short, there are simple ideas, of which no definition can be given; there are also axioms and postulates, in a word, primary principles, which cannot be proved, and indeed have no need of proof; and these are identical propositions, whose opposite involves an express contradiction. But there must also be a sufficient reason for contingent truths or truths of fact, that is to say, for the sequence or connexion of the things which are dispersed throughout the universe of created beings, in which the analyzing into particular reasons might go on into endless detail, because of the immense variety of things in nature and the infinite division of bodies. There is an infinity of present and past forms and motions which go to make up the efficient cause of my present writing; and there is an infinity of minute tendencies and dispositions of my soul, which go to make its final cause. And as all this detail again involves other prior or more detailed contingent things, each of which still needs a similar analysis to yield its reason, we are no further forward: and the sufficient or final reason must be outside of the sequence or series of particular contingent things, however infinite this series may be. Thus the final reason of things must be in a necessary substance, in which the variety of particular changes exists only eminently, as in its source; and this substance we call God.”

Alexander Pruss picked out the key ideas from Leibniz’s argument and put it in the following, succinct form (The Blackwell Companion to Natural Theology, The Leibnizian Cosmological Argument, by Alexander R. Pruss, pp.25-6):

Leibniz speaks of “an infinity” of “present and past forms and motions” of “minute tendencies and dispositions”. Basically an infinity of contingent facts. We can lump all these contingent facts into one, the logical conjunction of all contingent facts. This conjunction of all contingent facts has been called the Big Conjunctive Contingent Fact (abbreviated BCCF). Because all these facts are contingent and because their sum total is contingent it all requires explanation. But the explanation for all contingent facts cannot itself be contingent, otherwise it would be among the very set of facts in need of explanation. As Leibniz says, “the sufficient or final reason must be outside of the sequence or series of particular contingent things”. So this explanation must be the opposite of contingent, i.e. necessary. And Leibniz proposes that we call this God.

Like most arguments for the existence of God what is demonstrated, while important and significant, is also limited. There’s nothing demonstrated here about God’s activity in history or as revealed in scripture. It doesn’t tell us which religion or which sacred scripture, if any, is correct. It doesn’t tell us what kinds of ethical demands God might make of us. Such things might be demonstrated by other means and I think they very well can be. But that’s not where the argument has taken us so far. I think this is important because one actually doesn’t need to be religious to be a convinced theist. Being a Christian involves a lot more than this. For one thing it usually, and maybe always, involves transformative spiritual experience. Or one might be convinced just intellectually but in a way that would necessarily involve a great deal of familiarity with history, scriptural texts, and probably ancient languages. In modernity the reasonableness of theism itself is somewhat obscured by a lot of the cultural barriers, negative perceptions, and aversion to organized religion. But simple theism itself is fairly straightforward. I think theism is very rational and something that most people could easily accept, if not otherwise conditioned.

More later on the way that the principle of sufficient reason leads to an argument for the existence of God. Let’s first spend some time on the principle itself. Why accept it? What are some possible objections to it?

The best reasons for accepting the principle would seem to be indirect ones through arguments with a reductio ad absurdum form. Such arguments ask, what would follow if we rejected the principle? What would we expect the world to be like if everything did not have a reason? One thing we might expect is that it would be very common to find things and events that didn’t have any evident explanation or that were completely unintelligible. This would be very different from what we observe scientifically. It’s also just very different from the experience of regular life which is, well, quite regular. We just don’t see things happening or being certain ways for no reason at all. That’s what we could expect, let’s say, in the physical world. But it would go even deeper than this, into our minds and thoughts. The principle of sufficient reason pertains to connections between thoughts and ideas. We think one thing to be so by reason of some other thing and so on. But absent the principle of sufficient reason all of this is gone. We’d just have a bundle of thoughts and ideas without any way of structuring them to give support to one another and to know which ones to think are true and which are false. In other words, we wouldn’t be able to trust our own cognitive faculties.

Arthur Schopenhauer (1788 – 1860) distinguished between four forms of sufficient reason. Regardless of whether the four forms he picked out are the right ones or the only forms possible to pick out, I think that distinguishing between the different forms that sufficient reason can take is a good idea. Schopenhauer believed that philosophers throughout history had failed to make proper distinctions between various forms of the principle. In particular he thought most philosophers had failed to distinguish the other forms of PSR from the principle of causality, cause and effect in nature, which is only one form that the principle can take. Schopenhauer’s four forms were the principle of sufficient reason of becoming, knowing, being, and willing. These correspond to causality, rules of logic, mathematics, and motivations.

Causality is a major topic in philosophy with a whole host of objections and responses. Those are pertinent to PSR but, since causality is only one form of PSR, not to all forms of it. There are also objections to causality that are more properly objections to determinism rather than causality as such. For example, after the development of quantum mechanics we might think that many things happen without a cause. And we might similarly suppose that many things happen for no reason at all. For example, in radioactive decay the precise moment that any particular radioactive atom will decay is unpredictable. However the decay rate of many atoms of the same type over time is actually highly predictable, so that a given material has a characteristic half-life. A material’s half-life is consistent and related to its other properties. In more general terms the quantum state of a quantum system is characterized by a wave function. Under the Copenhagen Interpretation of quantum mechanics the square modulus of the wavefunction is a probability density. This gives the probability of different states being experimentally observed. Upon observation the wave function “collapses” into a single state. And we can’t predict with certainty which state will be observed.

Now this is certainly a different way of understanding how things work than we would otherwise have thought. But does it mean that things happen for no reason at all? I maintain that this is not the case because these events are still highly constrained and highly ordered. In quantum chemistry, for example, it is wave functions called orbitals that characterize the behavior of electrons in atoms and molecules. And yes, wavefunctions are inherently probabilistic. But the structure of these orbitals imparts tremendous explanatory power to chemistry at the level of atomic and molecular bonds, and consequently also to chemical reactions. I propose that it’s not the case that with the development of quantum mechanics we have found more things that happen for no reason at all. I think it’s the opposite. Before quantum mechanics chemistry was more dependent on macro-scale empirical observations of regularities. Although we could observe that certain chemical phenomena occurred regularly in certain ways we didn’t have as much understanding about why they occurred in the ways that they did.There was more arbitrariness in our explanations. But with quantum chemistry we have a much more developed understanding and we actually know more of the reasons why things happen the way they do.

Another important point is that although wave functions are inherently probabilistic in quantum mechanics this does not mean that the quantum states that are observed occur for no reason at all. That would only be the case if there were no laws of quantum mechanics. Then anything at all really could happen, without any kind of pattern. But such quantum phenomena do have a reason and that reason is the laws of quantum mechanics themselves.

Now returning to the way the principle of sufficient reason connects to the existence of God. A short description of the logic is that everything has to have a reason. Most things have their reason in something else. But ultimately all reasons have to lead back to one thing. And this one thing has to have very unique properties in order to be the reason for everything. For everything else and even for itself. The unique properties that this ultimate reason would have to have are those of God. Now to get into more detail.

The first important concepts to follow on to PSR are of contingency and necessity. If we grant that everything has to have a reason, cause, or ground the next step is to categorize the ways that they have these reasons. And there are two: contingency and necessity. A thing can have a reason in something else, which means it’s contingent. Or a thing can have its reason in its own nature, which means it’s necessary. And if we grant PSR there’s no third alternative.

Clearly almost everything is contingent. If you think of almost anything you can see how something else is a reason for it. And there are chains of reasons, as we see in a child’s relentless “Why?” game. Where a child asks some “Why?” question and follows up the answer with “Why?”, and follows up the next answer with “Why?”, over and over again. Eventually you give up answering, not because there is not a reason but because you don’t know what the reason is. This is a great illustration of contingency.

With these kinds of chains of reasons an issue that comes up is the infinite regress and the question of whether you can have an infinite regress. There are different opinions and arguments on that point but I think the possibility of infinite regress is untenable. William Lane Craig has done a lot of work on this subject. I also like what David Bentley Hart has called the “pleonastic fallacy”, which he defines as “the belief that an absolute qualitative difference can be overcome by a successive accumulation of extremely small and entirely relative quantitative steps.” (The Experience of God, 98) As it pertains to the case at hand, the difference between an infinite regress and a finite regress is an absolute qualitative difference. A finite regress terminates at some determinate point. An infinite regress does not. That’s an absolute qualitative difference. An infinite regress of reasons still lacks an ultimate reason. It doesn’t matter that there’s an infinite number of them. That’s the idea behind the joke that “it’s turtles all the way down.” If the world rests on the back of a turtle that rests on the back of another turtle and so on you can always ask what the next turtle is resting on. And it doesn’t help to say that it’s turtles all the way down. The stack of turtles is still unsupported. It doesn’t matter that there’s an infinite number of them. There has to be a termination in the chain. And that termination point has to be something with a unique set of qualifying properties.

So much for contingent things. What about necessary things? What would a necessary entity have to be like? There are reasons to think that a necessary being would have to be:

A word on actuality. Actuality and potentiality are concepts going back to Aristotle and the Medieval Scholastics. An entity can have some attribute actually or potentially. Actuality is an entity’s already having an attribute. Potentiality is an entity’s capacity to have an attribute. Almost everything has both actuality and potentiality for different things. Since things are certain ways they have actuality for those ways that they are. But they also have potentiality for all the ways that they are not yet but could be. There’s a connection here to contingency. If a thing could be many different ways but happens to be only certain of those ways, the ways that it happens to be are contingent, because it could have been otherwise. When an entity has potentiality for an attribute that attribute can only become actual if it is actualized. And it can only be actualized by another entity that has that attribute already, i.e. has actuality for it. Heat is an illustrative example. All materials have a certain heat capacity, which is the amount of heat they can absorb for a given increase in temperature. Materials have this capacity even when they are not increasing in temperature. In order to increase in temperature the material has to receive an energy input from some heat source. The heat source has actuality that it imparts to the material, actualizing its potential for the higher temperature. This is a physical example but the principles of actuality and potentiality also apply to ideas.

What are the reasons to suppose that a necessary being would have to be purely actual, noncomposite, and self-subsistent? A necessary being is one that cannot not exist. A contingent being is the opposite because it is possible for it not to exist and for it to have been otherwise than it is. Because a contingent being could be otherwise than it actually is it has unactualized potentiality. A necessary being cannot have unactualized potentiality. It has to be purely actual. The way it is is the only way that could be. Furthermore, all other things ultimately trace their source of actualization back to this necessary being. A necessary being is purely actual and also the entity that actualizes everything else. A necessary being has to be concomposite because anything composite could have been composed differently. Anything composite is composed of parts. These could be physical parts or abstract parts. Anything composed of parts cannot be necessary because it is possible for its parts to be put together in different ways or not at all. Finally a necessary being has to be self-subsistent in its existence because if it depended on some other entity for its existence it wouldn’t be self-subsistent.

In a previous episode, An Argument for the One, I shared a Neo-Platonic argument for why an entity possessing these attributes would have to be unique. There can in principle be only one thing which is purely actual, absolutely simple or noncomposite, and something which just is subsistent existence itself. Why is that? If there were more than one necessary being each would have to have some differentiating feature that the others lacked. Otherwise they would just be the same entity. But to have any differentiating features they would have to have potentialities. The potentialities of each would be whatever features the others did not have. But since a necessary being is purely actual it cannot have any such potentialities and so no differentiating features. This would preclude there being any more than one. So there can be only one necessary being.

It’s worth noting here for a moment that these attributes that the one necessary entity would have to have preclude certain candidates that might naturally occur to us. The big one, I think, is the universe itself. Can’t the universe itself just be the one explanation for everything? But this won’t do because the universe lacks the qualities that a necessary entity has to have. The universe is not necessary; it’s contingent. It doesn’t have to exist. The universe is not purely actual, noncomposite, or self-subsistent. The universe has many unactualized potentialities, potentialities that we know a lot about now thanks to the science of cosmology. The universe is certainly not noncomposite. The observable universe is thought to contain 10^80 particles. So the universe does not qualify as the kind of thing that could be the one necessary entity.

If we grant the foregoing there are also reasons to think that a necessary being would also have to be:

These are clearly attributes associated with God. At this stage we’re looking at identifying the one necessary being with the attributes of God. Why would a necessary being have all of these attributes? These trace back to its being purely actual, noncomposite, and self-subsistent. Immutability is changelessness, which relates to actuality and potentiality. Things with potentiality have the capacity to change. But something that is purely actual is already fully actualized. It doesn’t have any potentialities that need to be actualized. Such changelessness also applies across time. Because God is the same across time he is eternal, the same at all moments. God is also immaterial and incorporeal because he is noncomposite. Matter and bodies are essentially composite, both because they are composed of particles and because matter is a plurality; there are many different material and bodily entities, each with distinguishing features. God, being noncomposite, cannot be like that.

Because God is pure actuality and doesn’t have any potentialities that need to be actualized he is already perfect. He’s already everything that he can be. This perfection includes moral perfection. For the one necessary being to be fully good is actually the attribute that is, on its face, least obvious to me and also the one of greatest existential concern. Apart from all the foregoing, it would be easy for me to imagine that the ultimate source of all things with all power might not be morally good but might actually be amoral. And that would be rather distressing. Maybe morality is a human invention and not pertinent to the one necessary being behind all things. But in relation to everything else we can reason about God there is good reason to think that the one necessary being is also fully good. The goodness of the necessary being relates to his pure actuality. To see the relation requires a certain understanding of goodness. In this understanding goodness is the actualization of an entity’s potentialities. This is the understanding of goodness expounded by Aristotle and articulated in modern times by Alisdair MacIntyre. The good is that at which things aim. Living things have natures with potentialities to become the kinds of things that they are meant to be. Goodness is the actualization of these potentialities. It’s essentially creative and fruitful. Its opposite, evil, is essentially destructive and privative. We think of something like the Holocaust as the ultimate evil, and very rightly so. This was supremely destructive and the complete opposite of creation, multiplying, and replenishing. Other evils may be much less total in their destructive force but also work against growth and realization of our potentialities. The one necessary being is decidedly on the side of creation and goodness. As pure actuality God is the very source of all creation and growth that empowers all entities to move toward the things for which they aim.

Omnipotence is another way of understanding God’s pure actuality. Actuality means making things happen, which is essentially what power is. Everything that happens and that can happen is dependent on being actualized by the ultimate actualizer, and so God is the source of all power and is all-powerful.

Intelligence and omniscience are probably the most bold assertions about God’s nature. We might imagine a single source for all things but still resist that this ultimate source itself possesses human-like consciousness. Why should we suppose this to be the case? The reason for this relates to an important Platonic insight about the nature of reality. And this is the existence of abstractions. I discussed this in another episode about an argument for the existence of God from eternal truths. Examples of abstraction include mathematical concepts and theorems that would seem to hold independent of anything physical. Abstractions have the character of ideas. They can certainly subsist in our minds. But they would also seem to transcend any particular, finite mind, like the minds of human beings. These abstract forms can be actualized in the physical universe, as in the form of physical laws or in the form of created entities. As Edward Feser has stated: “To cause something to exist is just to cause something having a certain form or fitting a certain pattern.” (Five Proofs of the Existence of God, 33). If these abstractions have real existence they have to exist somewhere. The various modes of subsistence they might have is a huge topic but for our purposes here we’ll just note that as entities of a mental character the most reasonable way for them to exist is as ideas in God. It is the intellectual and mental nature of these abstractions, existing in God, that gives reason to think that God must have intelligence. In fact, his intelligence must be very great indeed because it comprises all abstractions. And because all actualization, including actualization involving these sorts of mental abstractions, originates from God, God’s intelligence must be all-encompassing; in other words, omniscient.

Let’s return to the expression of all these ideas in the forms of arguments for the existence of God. I shared earlier the argument from Leibniz, as re-expressed by Alexander Pruss:

This is a nice, concise argument. But a longer argument has the benefit of explaining a little more that is taken for granted here. For example, why we should understand a necessary being to be God and to have the attributes traditionally associated with God. The kinds of reasons I’ve been discussing. A longer version of the argument that lays all this out is given by Edward Feser in his book Five Proofs of the Existence of God, in his fifth proof which he calls the Rationalist Proof, since Leibniz was a rationalist. It proceeds in 27 steps. The terms and ideas should be familiar now after everything discussed so far. The argument is the following:

Feser’s argument covers the core points of the argument from the principle of sufficient reason as well as all related issues, tying this not only to God as the one necessary being but also to God with all of his classical divine attributes.

Now to speak more reflectively on all of this, I sometimes feel like we are all far too incurious and complacent about our existence. We’re all just thrown into life as infants without the ability to reflect on it and ask what should be a pretty obvious question: “What’s going on here?!” By the time we’re old enough to speak and reason we settle in and just go along with things. But we can still go back to the beginning, before we’ve taken everything for granted, and ask: “Where does all of this come from?” And there are important related questions like, “What’s our part in all of this?” “What are we supposed to be doing here?”

Maybe these are unreasonable questions to ask. But I don’t think so. Things don’t just happen for no reason at all. It may be practical to ignore these questions in order to just get along with the daily business of our lives. But we shouldn’t push them off forever. We are made for more than just our particular day to day affairs. The big questions are also the ones that give intelligibility and meaning to our life’s details.

The reason to believe in God is also the reason for asking for reasons for everything and anything at all.