Thought that has been thought out

Philosophy is merely thought that has been thought out. It is often a great bore. But man has no alternative, except between being influenced by thought that has been thought out and being influenced by thought that has not been thought out. The latter is what we commonly call culture and enlightenment today. But man is always influenced by thought of some kind, his own or somebody else's; that of somebody he trusts or that of somebody he never heard of, thought at first, second or third hand; thought from exploded legends or unverified rumors; but always something with the shadow of a system of values and a reason for preference. A man does test everything by something. The question here is whether he has ever tested the test. 

G. K. Chesterton, in The Common Man