I’ve been making a little bit of progress in recent months when it comes to arguments for God and the path to a reasonable theism, because I have finally started to see ways of breaking tie between a finite and an infinite past causal series. Every caused object is, it seems, the result of a causal series. If each causal series is infinite, there is no first cause (and arguably no God), but if at least one causal series is finite there is / has been at least one object (the first member of the finite series) that is not caused by another object. Such an object would have interesting features. It has / had some degree of power (the power to bring about the next member of the series) and it exercised that power in an unusual way (it wasn’t caused by something else to cause the next member). Further, it is either somehow caused by itself (which is difficult to understand) or entirely uncaused (which is also strange). Moreover, if its existence is not in some sense necessary (i.e. it must exist in this possible world or it must exist in some but not all possible worlds or it must exist in all possible worlds), then it seems the existence of the caused object ultimately becomes inexplicable (it is a result of something which needn’t have existed).

Now, one might try to avoid such strange objects by theorising that all past causal series are infinite, but that involves postulating infinitely many things to explain the existence of caused objects. That seems a bit excessive considering that we could explain all caused objects with only finitely many things. For example, all caused objects could be said to have a finite causal series which eventually goes back to one and the same first cause (a simpler, or at least less ontologically heavy, theory than the theory that there are distinct finite series which each have their own unique first cause, meaning that there are multiple first causes). More problematically, (at least some) infinite past causal series are themselves strange and it is not entirely clear that causation via an infinite past causal series is even possible if the members come into existence one after the other. Consider the following: If a caused object is caused by a past infinite causal series in which each member comes into existence through the prior causation of the member before it (the sort of infinite causal series that we typically think of as an alternative explanation of caused objects), then an infinite number of things need to have happened before one gets to the caused object. But it seems an infinite number of things cannot have happened. If you need to read an endless number of pages before you get to the end of a book, then it seems it is impossible to get to the end of it.

But there are admittedly also some difficulties with, or at least difficult questions about, the causation of the first cause. First, does it always (as long as it exists) cause the next member to come into existence? If so, does the next member always exist alongside the first cause (being always caused by it)? If not, why does the first cause start to cause the next member? Now, perhaps a certain arbitrariness can be avoided if the first cause has to go through a number of steps to cause the second member. In this way, the second member being co-existent with the first cause can perhaps also be avoided (there was a time or at least state when it was not). Second, is the whole causal series in some sense necessary (such that every member either must exist by itself or must exist because it follows necessarily from the preceding cause) and if not how does the (coming into) existence of some members not become inexplicable? The trouble is that if every effect follows necessarily and the first cause necessarily exists and necessarily causes the second member (exists in all possible worlds and causes the second member in all possible worlds), then it seems it is impossible that the effects never exist (there is no possible version of reality in which they do not at some point exist).