In WhatIsGoodOoCode I brought up LateWittgenstein while talking about definitions and measurability.
A quote gleaned from someplace off the web:
How should we explain to someone what a game is? I imagine that we should describe games to him, and we might add: "This and similar things are called 'games'". And do we know any more about it ourselves? Is it only other people whom we cannot tell exactly what a game is? - But this is not ignorance. We do not know the boundaries because none have been drawn. To repeat, we can draw a boundary - for a special purpose. Does it take that to make the concept usable? Not at all! (Except for that special purpose.) No more than it took the definition: 1 pace = 75 cm. to make the measure of length 'one pace' usable. And if you want to say "But still, before that it wasn't an exact measure", then I reply: very well, it was an inexact one. - Though you still owe me a definition of exactness.
The main thread of LudwigWittgenstein's thought after TractatusLogicoPhilosophicus was quite different from what had gone before. Thus, LateWittgenstein. LateWittgenstein wrote PhilosophicalInvestigations?, from which the above quote was taken. (69)