What is meant by the Taoist quote, "Those who know do not speak. Those who speak do not know?"
What this means is "failure," the failure of the Eastern tradition to take on the really hard task of at least trying to understand what Being or Tao or Tathagata or whatever you want to call IT actually is.
Let's contrast the failure of the Eastern tradition to even try to understand, with the brilliant, revolutionary, transformative and at least partly successful Pythagorean idea that the stuff of which everything is made is "Number." I say "partly successful" because Pythagoras had no knowledge of binary i.e. base two math. Had he been better equipped in this respect he could easily have taken the more advanced step of understanding that math is actually logic and so increased our understanding of the stuff of which everything is made to include consciousness. Hegel summed it up quite nicely when he added "The real is rational and the rational real." How much more enlightening is that than abjectly saying "Those who know do not speak. Those who speak do not know?" or Gautama Buddha saying, “Sink not the thread of the mind into the unfathomable?” Please.