"Those who are supposed to know but do not act simply do not know."?

[Stephus Kraius]

This is a quote from neo-Confucian Wang Yang-Ming.

To what extent do you think this notion holds true? Wang is claiming that when a person acts badly it is sure evidence that he or she does not really know what is good.

I have some ideas of my own, which I might add later, but I don't want to influence anyone as I'm interested in what you have to say.
Well, I think that the first step toward an answer is elaborating on the relationship between knowledge and action.

Wang appears to equate the two in that when one knows what is right, one will act accordingly in a way that manifests what he or she knows to be good in the action taken.

To refute this claim one must find an argument that separates knowledge from action. It seems like what would keep the two from being synchronized is an obstruction - either internally or externally.

Internally, one may simply not be strong enough to act upon knowledge of the good. Weakness of the will, and fear (like Barbara E proposes) could achieve this.

External restrictions may also play a role. If you know it is good to save a particular species of animal, after reading a book about it, let's say, but are locked in your house by your abusive parents, then you simply cannot act if you aren't given the chance.

But then, does true knowledge of just action not inherently imply action?
Yaoi, thank you for your response, and I appreciate that you point out the effect of punctuation on the meaning of a sentence.

The quote, however, is taken directly from a translation of Wang - it is not mine. And I have clarified exactly what I meant (and what Wang meant - "Then you tell us what Wang meant.") by stating that:

"Wang is claiming that when a person acts badly it is sure evidence that he or she does not really know what is good."

Did you not read this part of my question, or is your confusion extended to this part as well?