5, 8, 11, 14, 17…  What’s the rule?  What’s the concept?  That’s the question that Socrates asks Euthyphro and perhaps repeatedly the question of philosophy.  “What is piety?”, Socrates asks.  “Piety is doing what I’m doing now, prosecuting the wrongdoer”, Euthyphro responds.  “But I didn’t ask about this or that version of piety, but piety itself!  Certainly there are other things that belong to piety!”, Socrates rejoins.  He wants to know the rule behind all the instances of piety:  prayer, sacrifice, prosecuting the wrongdoer, funny hats and outfits, treating certain things as sacred, observing certain sacred days, dietary requirements, and all the rest.  5, 8, 11, 14, 17…  “You’ve given me a list, what’s the concept?”  Knowledge for Socrates (or Plato?) is the concept.  What’s the concept behind the diversity of 5, 8, 11, 14, 17…?  It’s a simple rule:  F(x) = 3x + 2.  Plug in a value 3 into x and you get 11.

Now we know the concept.  If I plug in 6 I can play the game.  The result will be 20.  The prisoners in the cave play the guessing game.  What image will appear in the wall next?  The prisoner escapes and returns.  He can guess the next image in the series with uncanny accuracy because he knows the concept behind the images, the rule.  Plug in 7 and you’ll get 23.  20 came before, so now we get 23.  There’s a sort of Lacanian Real at work, a repressed.  The secret number of the game is always repressed:  first 6 and then 7 (generating 20 and 23).  They never appear.  But they’re the cypher that functions as the input that generates the output:  20 and 23.  A whole hermeneutics of suspicion!  A secret number that makes another number manifest.  So there are two features of the concept:  the function that is the rule and the secret number put into the function that generates the outcome of the rule.  4 and 14.  Socrates (in Plato’s version) wants to know the rule behind the series and the secret cypher or input that generates the result.  That’s the dream.  That’s the reality/appearance, essence/existence distinction.