One of the troubling features of a first cause is that, seemingly, it must be self-explanatory in some sense, if the whole of reality is explicable. Now, perhaps one thinks we can avoid self-explanatory / internally explicable beings by holding to the view that there is no first cause but rather a causal series that stretches infinitely into the past. But that is not quite as easy as one might think:

1. An infinite causal regress exists which is fully caused by its parts and features.
2. If the existence of an infinite causal regress is fully caused by its parts and features, then its existence is self-explanatory or internally explicable.
3. Therefore, there exists something that is self-explanatory or internally inexplicable.

Moreover, we can also put forward a Rasmussen-style argument for the existence of something that is internally explicable:

1. The whole of reality is explicable.
2. If (1), then the whole of reality can only be internally explicable, since there is nothing outside of the whole of the reality by which it can be explained.
3. If (1) and (2), then the whole of reality is internally explicable.
4. Therefore, something exists which is internally explicable.

It thus seems we must admit that there is something that is internally explicable, or give up the view that reality is fully explicable.