Next, by “cause,” I'm not referring to a strong version of the Principle of Sufficient Reason (PSR). Instead, I'm using what might be termed a minimal version of the principle (M-PSR). The M-PSR does not exclude indeterminism; it merely stresses that being cannot arise from non-being, that something cannot come from nothing. So, for example, quantum fluctuations may be “uncaused” in the sense that they're random, but they're still caused in the sense that they are dependent on the energy contained within the quantum vacuum. In other words, quantum fluctuations come from something, rather than nothing, and are caused in that sense.
To sum up my initial thoughts, I'm arguing for a first cause in the sense that the universe has some sustaining cause. One can accept this without believing that the universe was created at some moment in the finite past.
We may summarize the argument, then, as follows:
1. Every dependent thing has a cause.
2. The series of dependent causes either proceeds to infinity, or has a self-existent first cause.
3. The series cannot proceed to infinity.
4. Therefore, there exists a self-existent first cause.
From experience, we all know what (1) is saying. Take the human body, for instance. The human anatomy is dependent on its systems, its systems on organs, its organs on cells, and so forth. The human body is also dependent on external things like oxygen, etc. Cells, then, cause organs insofar as organs are dependent on cells. Hence, X is a cause of Y, so long as Y relies on X.
(2) simply puts forth our available conclusions. Either the hierarchy of causes proceeds to infinity, or else it has a self-existent first cause. Something is self-existent if and only if it exists by a necessity of its own nature. The reason the first cause would have to be self-existent is because it would be impossible for it to be dependent. If it were dependent, then it would be caused by something else; and hence, it wouldn't be first, which is a contradiction. Moreover, to say that the first cause is dependent, but isn't caused by something else, is an instance of special pleading.
Our third premise asserts that an infinite series of causes is impossible. In support of this, we might note that the series of dependent causes will be causing something at any finite period of time. However, it would take infinite time for an infinite series of causes to do anything. Therefore, the series itself must be finite.
This confirms an inductive argument we can formulate about the necessity of a first cause. For, whenever we remove the first cause of some series, it is inevitably the case that we end up removing the secondary causes. For example, if a house didn't have a foundation, then it would collapse, no matter how many parts of the house there are. Likewise, if there were only dependent things, and nothing self-existent, then nothing would exist.
As a result of the series of causes being finite, we can only conclude that it has a self-existent first cause. Objections like, “what if time were infinite?” are irrelevant, since the argument is perfectly consistent with an infinitely old universe. The only claim being made is that the ontological series of causes cannot proceed to infinity. With that said, I believe this is a strong argument in favor of a first cause, even if one believes the universe is infinitely old. Aristotle took this position, and it is one that I personally believe is a good starting point in our discussions about metaphysics, God, and the order of things.
The question for us now is this: why should the universe have only one first cause? I believe the first cause's uniqueness can be inferred from the uniformity of nature. If, in fact, there were more than one first cause, then we would expect one set of things to behave in entirely different ways than another set of things. Yet, everything that exists is at the very least intelligible, if nothing else. This means that everything that exists participates in the singular attribute of intelligibility, which is best explained by one first cause, rather than many. Remember, we're talking about uniformity, and not pluriformity. The first cause must also be eternal, since it cannot depend on anything else at any time. If it were to come into existence, or go out of existence, then it would depend on whatever conditions were necessary for that state of affairs.
Overall, then, I believe this version of the cosmological argument successfully demonstrates the existence of a self-existent first cause of the universe. Moreover, it adequately shows that the first cause is both one and eternal. In a later post, I'll put together some thoughts on why this first cause is plausibly God. In other words, I'll attempt to show that the first cause has attributes that are most consonant with the God of classical theism.