We are all familiar with the closing scene of Plato's Phaedo and the last sentence of Wittgenstein's Tractatus, of course. But I think this is pretty damn good, too:
Is it not odd that men should have come to this pass--that they look for hope in physics and welcome, as some do, any indication of unreason in the world? Perhaps it seems less odd when we reflect upon the history of mankind, the hopeless mess that we have made of human lives. Our greed, our stupidity and lack of imagination, our apathy, these are the factors upon which the present sorry state of the world is largely consequent. It is enough to fill us with depair. Yet, despair need not be the last word. It lies within our power, if we so desire, to make the familiar world we inhabit more worthy of habitation by beings who aspire to be rational and are capable of love. Our limitation is due not to ignorance, not to the 'blind forces of Nature', not to the astronomical insignificance of our planet, but the feebleness of our desires for good. This limitation is not to be removed by the advances of physical knowledge, nor should our hopes be placed in the researches of the physicist.--L. Susan Stebbing, Philosophy and the Physicists.
Some other time I'll blog more about Stebbing (recall my exchange with Mohan (here, here, and here); Mohan and I have done some follow-up work), but for now let me ask readers for their favorite closing lines of philosophical works.