The Ontological Argument

The ThinkerLast week, I reviewed some key terms in logic as a prelude to looking at logical arguments for the existence of God. This first one is a philosophical rationale called the ontological argument. Ontology is simply the study of existence, or reality. And so the ontological argument is a line of reasoning based on the very nature of existence.

The first premise, or basis for this argument, is that it is at least possible that a maximally great being exists. This isn’t about what’s probable at this point – just what’s possible. It’s also not about whether we can know whether this being exists or not (epistemology), but simply about whether it could exist (ontology) . Now let’s define some terms. A “maximally great being” can be defined as a being possessing omniscience, omnipotence, and moral perfection. Omniscience is knowing all truth and only truth. Omnipotence is the ability to cause any effect not logically impossible. It is necessary, or noncontingent, existence. Moral perfection is the highest degree of moral attributes such as love, mercy, justice, etc. Where attributes conflict (i.e. mercy vs. justice), this being possesses the greatest compatible degree of each, such that any more of either trait could be considered an introduction of imperfection (i.e. the best possible combination). There is nothing self-contradictory about this concept. It is not like a square circle or a married bachelor. It is simply the spectrum of characteristics we observe in human beings extrapolated to a maximum value.

Premise 2 is that if it is possible that a maximally great being exists, then a maximally great being exists in some possible world. By “possible world”, we do not simply mean another planet, but rather any alternate reality with its own forms of matter & energy, laws of physics, existence or nonexistence of life, and even existence or nonexistence of space-time itself. The set of all possible worlds would be a set of all possible versions of reality; each with one, and only one, variable different from all others. For instance, one possible world may have a slightly different gravitational constant that results in the collapse of any conceivable universe, or the impossibility of the universe ever forming. Another might have every physical variable identical to the reality we are familiar with, but with a history where Hitler won WWII. This set of possible realities is necessarily immense (practically infinite) to address every possible physical and historical alternative.

Premise 3 proposes that if a maximally great being exists in some possible world, then it exists in every possible world. This one isn’t a very intuitive step, so let’s look at it a little closer. If a maximally great being in a possible world is indeed omnipotent, then all else in that possible world is contingent, or dependent on its existence. If it is morally perfect, then it is capable of making conscious decisions, of exercising free will. In that case, this being could’ve chosen not to create anything, but simply to exist, alone. So if a maximally great being exists, there is a possible world such that only that being exists. This would then be the minimum qualification for a possible world. This being is then the “lowest common denominator” in all possible worlds (i.e. one variable in common to all, that cannot be negated without eliminating that world from the set of all possible worlds). Therefore, Premise 3 logically follows, and the maximally great being exists in all possible worlds.

Premise 4 states that if a maximally great being exists in every possible world, then it exists in the actual world. What applies to the set as a whole applies to all members of the set. In logic, this is called “dictum de omni”, or the law about all – whatever is universally true of a subject must be true of everything contained in that subject. The actual world is contained in the set of all possible worlds. Therefore, premise 4 logically follows.

Premise 5 simply adds that if a maximally great being exists in the actual world, then a maximally great being exists. Not too controversial. The actual world is what exists as opposed to possible worlds that only could exist. Anything shown to exist in this actual world therefore has actual existence.

From these 5 premises follows the conclusion that a maximally great being exists. At this point, we’ve simply concluded that some being with certain characteristics necessarily exists, but what do those characteristics tell us? A necessary or noncontingent being can exist outside of space and time and is therefore immaterial. An omnipotent being could create, or cause all contingent elements of reality to exist. An omniscient being would be capable of designing the incredibly complex and very interdependent “system of systems”  we recognize as our universe. A morally perfect being would have the authority to issue decrees, judge behavior, and reward or punish as appropriate. This description aligns remarkably well with the biblical description of God, which leaves the reader with the choice of trying to refute the argument or admitting the existence of God and dealing with the consequences. Choose wisely.


Reasonable Faith, 3rd Ed., (Crossway Books, 2008), by William Lane Craig, Chapters 3 & 4. Craig’s interpretation of Alvin Plantinga’s refinement of St. Anselm’s ontological argument was a major part of my giving this argument another chance after discounting it for years. My only departure from Craig is that in premise 3, I’ve tried to justify the jump from existence in a possible world to existence in every world without resorting to the modal logic used by Plantinga and Craig.

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