4 ideas
Real knowledge already contains action: to know filial piety is to already be practicing it, just as seeing a beautiful color and loving it happen in one moment. Someone who says they know the good but does not do it does not yet know it; the split between knowing and doing is a symptom of selfish desire blocking the original unity, not a gap that more study can close.
As a young man, Wang took Zhu Xi's instruction to 'investigate things' literally and sat before bamboo in his courtyard trying to extract its principle, until he fell ill after seven days without insight. He concluded that principle cannot be found by probing external objects; 'investigating things' must mean rectifying the mind's own intentions toward things.
Every person has a built-in moral knowing that immediately registers right and wrong without deliberation, the way anyone instantly feels alarm at a child about to fall into a well. Cultivation is not acquiring new moral knowledge but 'extending' this faculty, clearing away the selfish desires that obscure it so it can act fully in each concrete situation.
Asked whether a flower blooming alone on a mountain has anything to do with the mind, Wang answers that before you looked at it the flower and your mind were both in stillness, and when you looked its colors became clear at once. This lens treats meaning and principle as arising in the meeting of mind and thing, so 'mind is principle' means there is no order of value standing apart from a perceiving, responding mind.