How do we interpret this? Do we think about it as a perfection of everything involved in a painting? The idea, the method, the interpretation? The oneness of the artist with her culture?
The second principle is interpreted as 'the bone' of the work. Herbert Read says this is to do with the structural strength of the brushstroke, the 'skeleton' of the work. My feeling is that it is to do with the skill of the artist being at one with the artist. It is unity and therefore strength given thereby. It has to do with fluency and the well practised becoming instinctive.
The third principle is to do with appropriate form. 'A correspondence between subject and form'. I think, idea and form. Again, they are one, united, perfect unity.
The fourth principle is about colour. I guess, the right colour. Again a total appropriateness to the subject and the feel to be given.
The fifth principle is about composition - everything in its place and a place for everything. This might include perspective. It includes giving importance to the subject matter in where it is in relation to other elements. It is good composition, which is in the trained and experienced eye of the practitioner.
The sixth principle is about 'copying'. I wonder if this means, not copying nature, or copying a face but more to do with interpretation, with all the previous elements in their perfect state; ' copying' the influences that went into the inspiration in the first place; a 'picking up' by the artist of the elements in the culture that flow through the artist's hands to have a perfect expression outwards, of what went inwards.