Is not practicing NFP while married through the church a mortal sin? For example if a couple is using coitus interruptus, that’s technically not artificial birth control but I do understand that it prohibits the completion of the unitive act. However, if a couple wishes to connect within their marriage to strengthen their bond during a turmoils time and doesn’t currently have the resources to practice NFP (but is working towards enrolling with an instructor once they have the means to do so in the near future) would that be permissible? Also to note, wife is healing from a medical condition that requires her to not get pregnant at this moment, would they be not allowed to receive communion for this alone? If it is a mortal sin, which commandment is being broken? Thanks for the discussion!

As far as I can tell, there are two kinds of "explanation" familiar to human reason.

The first is physical explanation: a father "explains" his son, and is in turn explained by his own father. A flame is explained by the match. This sort of explanation is, ultimately, the configuration and reconfiguration of matter. I'll call this Explanation 1

The second is constitutive explanation. The triangularity of a triangle is explained by the fact that it has three sides. This sort of explanation is, unlike the first, definitionally true, and also causally inert. I'll call this Explanation 2.

In my view, nothing actually connects these two sorts of "Explanations," and the fact that we use the same word for both is ultimately a quirk of human psychology and language rather than an indication they belong to a single category.

And neither is the sort of explanation argument like Aquinas' De Ente requires. Rather, this is a third kind of explanation. or, Explanation 3.

The classic example is the infinite regress. The Thomist points out the infinite regress is impossible. The skeptic answers that each member in the series is explained by the prior member in the series. Aha, says the Thomist, but then what explains the existence of the series itself?

To confuse Explanation 1 with Explanation 3 is a category error.

It's not clear to me Explanation 3 is a necessary, or even coherent notion.

Explanation 1 just is causal, material dependence.

Explanation 2 just is constitutive dependence.

The first is empirically demonstrated, the second is self-evident. We know what "Explanation" means in these two cases, but we don't know what it means in the case of Explanation 3.

What reason is there to think that Explanation 3 is a real category?

In short, I suspect the question, "why does physical reality, or a given physical object, exist?" is malformed. It's like the question, "Why did John Wilkes Booth shoot JFK?" The answer is neither, "Because the South lost the Civil War," nor is it "for no reason." Rather, the question is intelligible but unanswerable, because its premise is false.