For most of us, first principles operate in the background and may be inherited from tradition and common sense. As Edmund Burke pointed out, life would become impossible if we tried to think through every new situation from first principles from a blank slate, disregarding both our own experience and the wisdom of our culture.
Other aspects of first principles can only become to be known through an illative sense. This is John Henry Newman's notion as how we go about making primary judgments; not just from reason and logic, but many fragments of experience that distill into a single and unified conviction. This includes an accumulation of our sentiments, observations, tradition, imagination, intuitions, and instincts.
While these are deeper convictions, we can never have complete certainty of them. Besides, certainty never belongs to the mind. If we are blessed, we can be certain of Truth in our heart, but only have certitude (or sureness) once we speak of it. First principles have the ring of Truth, but are not Truth in itself.
Think of these principles like an asymptote—a line approaching a given curve, but never quite getting there while going on for infinity. All we can do is aim for some coherence that vibrates higher as we approach the horizon. Without coherence, we will falter from Truth even further. Poor principles, bad consequences.
This leads me to articulating my first principles that inform my life. I've taken these from a recent post by Edward Feser who states them so well; however, I did make some edits to massage these closer to my convictions. Here are the seven key principles:
1. The cosmos has a systematic unity, given by the divine that is both outside (transcendent) and within (immanent).
2. This unity reflects an explanatory hierarchy and in particular a “top-down” approach to explanation (as opposed to the “bottom-up” approach of naturalism), especially in the two key respects that the simple is prior to the complex and the intelligible is prior to the sensible.
3. The divine constitutes an irreducible explanatory category, and is to be conceived of in personal, as well as impersonal terms. The divine is relational and absolute—both triune and one.
4. The person also constitutes an irreducible explanatory category. We can't be reduced to nature or nurture.
5. Persons are part of the hierarchy and their happiness, as well as purpose, consists in recovering a lost position within it, in a way that can be described as “becoming like God.” [The quest, thus, has no external 'object,' but is reality itself becoming luminous for its movement from the ineffable, through the Cosmos, to the ineffable. — Eric Voegelin]
6. Moral and aesthetic value is to be analyzed by reference to this metaphysical hierarchy. The good and the beautiful are not relative, but universal. The divine is in all things, but to different degrees.
7. The epistemological order is contained with this metaphysical order. Truth is not relative, but universal. Once again, the divine is in all things, but to different degrees.Assuming you were a materialist and relativist, your first principles would reverse many of these statements. Everything would be reducible to nature (or nurture), and there would be no hierarchy or systematic unity. And your principles would have no coherence to explain intelligibility or higher order/values.
If you were an pantheist, everything equally would be an immanent spirit. But without a transcendent, there would no distinctions around a higher order/values nor would there be any motivation for “becoming like God.” There would again be a lack a coherence, as the world would mostly be explained away as an undiscriminating divine oneness.
First principles matter! So as they say: as above, so below.