The above position occurred in a 1934 game. That is, at the height of the New Fuseki phase.

Black started at tengen and has just played at the triangled point. In other words, he has ignored the principle of corners, sides then centre. This did not attract any comment from commentator Kato Shin, who was hardly a fan of New Fuseki.

White's next move was at A. Again, the c-s-c principle is being ignored. A first rationalisation might be that allowing Black to make a square moyo is not good - ok, chalk that up on the board as provisional. Kato didn't criticise it directly but said that B would be more usual. More support for the hypothesis that allowing a square moyo is bad. As to why the lower left is ignored, we can chalk up another associated provisional notion: Black's shape after the square moyo is allowed if White 6 is in the lower left is too strong, and White would then be playing close to thickness, whatever he did around that area (it's almost a toxic Chernobyl area).

But Kato then goes on to give a possible alternative for White 6: C or D, then Black a point above B, then White 7 at E. So it's OK after all to allow a square moyo and it's OK to play White 7 in a Chernobyl area. Demolition of hypothesis. Is this frustrating or is it frustrating?

Kato didn't comment on the unusual White shimari advocated for the upper right (and White did also play C in the game), but that was fairly common even in the 1920s, and before.

I always like to compare go to a language. And in language we also formulate principles as part of our effort to teach. "I before E, except after C", "Don't split infinitives", "Never end a sentence with a preposition", etc. And those principles are all very useful to learners, and mostly true, but they do not really survive contact with the realities of actual language. A native speaker instinctively knows what is right and what is wrong. A native speaker might think that a preposition might not be such a bad thing to end a sentence with, that it is nonsense to never split an infinitive, and that there are plenty of weird words where E comes before I even without a C.

Professionals are the native speakers of go. They might use principles to explain their choices after the fact, but deep down their choices are not actually based on such principles. A professional doesn't think "Corners, sides, center, so where do I play?", he plays the points that feels right.

So IMO principles are useful as a framework for learners, for amateurs that need a flotation device in the vast sea of possibilities. But beyond a certain point, they are no longer required. Partly, also, because they have become second nature.

Do we have a professional to verify what they think or do we just make claims like that? That they think on a higher, god-like level. Would it not be possible for someone to say "Yes, I think about these principles but I'm wise enough to know when to ignore it."?

Weak principles are overridden by stronger principles. Applied principles (below the level of perfect knowledge as theorems) need management for conflict dissolution. Since theorems exist, a general statement "Theoretical principles are useless." is false. It is good to see that there have been professionals who ignored (some of the) too weak principles.

Most people quote these because they have heard them, not because they understand them. There is no such constrictions in English. They were superimposed on the language by the adherents of Latin because they are true in Latin. Of course, Latin does not have that many prepositions as it uses inflexions so it is not actually possible in Latin. To quote Churchill: this is the sort of nonsense up with which I will not put.

In reference to John's post I have to wonder how many prinicples that amateurs follow in their games are actually superimposed artifically in a similar manner.

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Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).