Re: Baseline skillset
If you chase the word "subtle" down to its molecular level, or the etymological equivalent thereof, you will find that it is ultimately derived from "teks-", which also is the basis for words like tisse, context, architect, and, lo and behold, technical. That is why I used "subtle" instead of "insubstantial" or "ethereal"; principles are elusive, not because there isn't much to them, but precisely because there is so much.
Still, as Mike said above, principles are, "... fairly straightforward, just like a magic trick after someone shows you how it's done. THEN it gets subtle." Or, in Edisonian terms, that's where the 99% perspiration part kicks in.