Excerpt from "History of Madness" by Michel Foucault 10-12

So the ship of fools was heavily loaded with meaning, and clearly carried a great social force. On the one hand, it had incontestably practical functions, as entrusting a madman to the care of boatmen meant that he would no longer roam around the city walls, and ensured that he would travel far and be a prisoner of his own departure. But there was more: water brought its own dark symbolic charge, carrying away, but purifying too. Navigation brought man face to face with the uncertainty of destiny, where each is left to himself and every departure might always be the last. The madman on his crazy boat sets sail for the other world, and it is from the other world that he comes when he disembarks. This enforced navigation is both rigorous division and absolute Passage, serving t underline in real and imaginary terms the liminal situation of the mad in medieval society. It was a highly symbolic role, made clear by the mental geography involved, where the madman was confined at the gates of the cities. His exclusion was his confinement, and if he had no prison other than the threshold itself he was still detained at this place of passage. In a highly symbolic position he is placed on the inside of the outside, or vice versa. A posture that is still his today, if we admit that what was once the visible fortress of social order is now the castle of our own consciousness.
Water and navigation had that role to play. Locked in the ship from which he could not escape, the madman was handed over to the thousand-armed river, to the sea where all paths cross, and the great uncertainty that surrounds all things. A prisoner in the midst of the ultimate freedom, on the most open road of all, chained solidly to the infinite crossroads. He is the Passenger par excellence, the prisoner of the passage. It is not known where he will land, and when he lands, he knows not whence he came. His truth and his home are the barren wasteland between two lands that can never be his own. Perhaps this ritual lies at the origin of the imaginary kinship common throughout the culture of the West. Or perhaps it was this kinship that called for and then fixed the ritual of embarkation whose origins are lost in the mists of civilisation. But one thing is certain: the link between water and madness is deeply rooted in the dream of the Western man.
In the medieval romance of Tristan et Iseut, Tristan is put ashore by the boatmen on the coast of Cornwall, disguised as a madman. On his arrival at the castle of King Mark, he is recognized by no one, and no one knows where he has come from. But his conversation is too strange, distant and familiar, and he is too aware of the well-kept secrets of this world not to have come from another very close by. He is not from dry land, with its solid cities, but from the unceasing restlessness of the sea, whose unknown paths reveal such strange truths, that fantastic plain, the flipside of the world. Iseut is the first to realize that this madman is a son of the sea, and that he’s been put ashore by unrepentant sailors, making him a harbinger of bad luck: ‘Damn the sailors who brought this madman, would that they had thrown him in the sea!’ she cries. The theme reappears many times throughout the ages. For the mystics of the fifteenth century, it was the idea of the soul as bark, tossed on the sea of infinite desires, surrounded by sterile attachments and ignorance on all sides, and distracted by the meretricious sparkles of knowledge, in the midst of the great unreason of the world — a boat at the mercy of the great madness of the sea, unless he drops anchor on the solid ground of faith, or spreads its spiritual sails so that so that [sic] the breath of God might bring it home to port. In the late sixteenth century, De Lancre blamed the demoniacal calling of a whole people on the sea; the uncertain furrow of the wake, the exclusive trust placed in the stars, the secret knowledge that passed from mariner to mariner, the distance from women and the ceaselessly shifting plain of the surface of the sea made men lose faith in god, and cast off the shackles of their attachment to their homeland, thereby opening the door to the Devil and the ocean of his ruses. The classical era was content to blame the English melancholy on the influence of a marine climate: the cold, wet, fickle weather and the fine droplets of water that entered the vessels and the fibres of the human body made a body lose its firmness, predisposing it to madness. And finally, ignoring the huge literary tradition that stretches from Ophelia to the Lorelei, it is perhaps enough to quote the anthropo-cosmological analysis of Heinroth, where madness is the manifestation in man of an obscure, aquatic element, a dark, disordered, shifting chaos, the germ and death of all things as opposed to the luminous, adult stability of the mind.
So the ship of fools resonates in the Western imagination with immemorial motifs. But why then, towards the fifteenth century, do we get this sudden formulation of the theme in literature and iconography? What made the silhouette of the ship of fools and its mad cargo loom so large against familiar landscapes? Why, from the old alliance of water and madness, was this ship born, and what made it appear at that very moment?