From Friedrich Nietzsche, Human, all too Human, as quoted in Jurgen Pieters' very interesting book Speaking with the Dead: Explorations in Literature and History (Edinburgh UP, 2005):
I too have been in the underworld, like Odysseus, and will often be there again; and I have not sacrificed only rams to be able to talk with the dead, but have not spared my own blood as well. There have been four pairs who did not refuse themselves to me, the sacrificers: Epicurus and Montaigne, Goethe and Spinoza, Plato and Rousseau, Pascal and Schopenhauer. With these I have had to come to terms when I have wandered long alone, from them I will accept judgement, to them I will listen when in doing so they judge one another. Whatever I say, resolve, cogitate for myself and others: upon these eight I fix my eyes and see their eyes fixed upon me.--May the living forgive me if they sometimes appear to me as shades, so pale and ill-humoured, so restless and, alas! so lusting for life: whereas those others then seem to me so alive, as though now, after death, they could never again grow weary of life. Eternal liveliness, however, is what counts: what do 'eternal life', or, life at all, matter to us!