Outlined Version of the Contingency Argument

Here is an outlined version of Aquinas’s Contingency Argument for the existence of God, also known as the Third Way. This is just an outline. The full series of articles can be found here, here, and here. Refer to those for the whole, in depth explanations and defenses of the various premises.

The first part of the argument is to establish the existence of at least one necessary being. There are two branches of interpretation for this part. This is the first:

1. In our experience there are beings which are generated and corrupted
2. Beings which are generated and corrupted are “possible” beings (or contingent beings); they have the possibility to either exist or not exist
3. Possible beings have a natural tendency towards corruption (losing their form)
4. Given sufficient time, all natural tendencies are realized
5. Thus anything that has a natural tendency towards corruption will necessarily, at some point in time, go out of existence
6. If all beings were possible beings, then, given infinite past time, all beings would have gone out of existence by now
7. If all beings had gone out of existence, then nothing would exist now.
8. But things do exist now
9. So not everything that exists can be a possible being. There must exist something, at least one thing, which is impossible not to exist: a necessary being.

This is the second branch of interpretation:

1. In our experience there are beings which are generated and corrupted
2. Beings which are generated and corrupted are “possible” beings; they have the possibility to either exist or not exist
3. All possible beings were generated at some point in time
4. If all beings were possible beings, then all beings would have to have been generated at some point in time.
5. If everything (meaning the set of all existing beings) had to have been generated at some point in time, then before everything was generated, nothing would have existed
6. But if nothing existed, then there could be nothing to generate the set of all existing beings, and thus nothing would exist now.
7. But things do exist now
8. So not everything that exists can be a possible being. There must exist something, at least one thing, which is impossible not to exist: a necessary being.

Both of these branches of interpretation take us to the same point, and both, in my view, are defensible and compatible with each other. We have arrived at the existence of a necessary being, where do we go from there?

1. A necessary being is a being which, once it exists, is not ever generated or corrupted. A necessary being thus exists continuously and permanently; its natural tendency is towards maintaining its form in existence
2. Any being whose natural tendency is towards maintaining its form in existence, either has existence as intrinsic to its nature, or else has existence continuously “added” to its nature, sustaining it in existence
3. If the former, then the being has existence as identical to its essence, making it Subsistent Being Itself (which is what we call God)
4. If the latter, since the being continuously exists from moment to moment, it must have existence continuously given to/sustained in it from moment to moment
5. This latter case is the actualization of potency which takes place simultaneously each moment. This constitutes an essentially ordered causal series.
6. Causal series necessarily must either regress infinitely, loop circularly, or terminate in a first member
7. Essentially ordered causal series in principle cannot have an infinite or circular regress
8. An essentially ordered causal series of existence added to essence terminates in a first member which is Pure Existence, Subsistent Being Itself (as is established in the Second Way).
9. Therefore, the existence of any necessary beings requires the existence of Subsistent Being Itself

What can we know about this Subsistent Being Itself? (Much of this is repeated from the linked post on the Second Way).

1. Subsistent Being Itself is identical to Pure Act and First Cause
2. Pure Act has no potencies
3. Anything that changes has potencies
4. Therefore, the First Cause cannot change (is immutable)
5. In order to distinguish objects from other objects, they must have unrealized potencies
6. Two or more beings of Pure Act would have no potencies, and thus would be indistinguishable, and thus identical
7. Therefore the First Cause is one
8. All material objects have potencies
9. Therefore, the First Cause cannot be material (is immaterial)
10. To come into or go out of existence is to change
11. Therefore, the First Cause can never have come into, and can never go out of, existence (is eternal)
12. Every being which exists within time has potencies
13. Therefore, the First Cause cannot exist within time (is timeless)
14. Pure Act is the First Cause which ultimately actualizes all potencies, so it is the ultimate efficient cause of everything that happens
15. Furthermore, as Subsistent Being Itself, it is Pure Existence, and everything else that exists derives its very existence from it
16. Thus it can be said to be “all powerful” in the relevant sense (is omnipotent)
17. There are several arguments for the personhood/intelligence of the First Cause
    1. Argument from the Nature of Immaterial Beings:
       1. All material beings are composites of form and matter
       2. All material beings are capable of instantiating only one form at a time, because they are limited by their material nature
       3. An immaterial being would not be limited by material nature, and thus could instantiate multiple forms at once
       4. When an immaterial being instantiates multiple forms, it is said to grasp/understand/conceive of that form. This is what intellect is
       5. The First Cause is immaterial
       6. Therefore the First Cause has intellect
    2. Argument from Proportionate Causality:
    3. 1. All causes must contain their effects either eminently or formally
       2. The First Cause is the ultimate cause of all human attributes
       3. Therefore, the being of Pure Act must contain human attributes either eminently or formally
       4. Many human attributes are material in nature
       5. The being of Pure Act is immaterial
       6. Therefore, the being of Pure Act can only be said to contain these physical/material attributes eminently
       7. Some human attributes, such as personhood and moral nature, are immaterial
       8. Thus the being of Pure Act could be said to contain these attributes formally
       9. Therefore, we can say that the being of Pure Act contains personhood and a moral nature (albeit analogically)

Thus we arrive at one necessary being that is the First Cause of everything, that is Pure Act and Subsistent Being Itself, that from which every other being derives its very existence, which is immutable, immaterial, timeless, eternal, omnipotent, and personal. And this Being we can rightly call God.