<b>Grelet's solitary sailor is a radical theoretical figure, herald angel of an existential rebellion against the world and against philosophy's world-thought.</b><br><br>Over a decade ago, Gilles Grelet left the city to live permanently on the sea, in silence and solitude, with no plans to return to land, rarely leaving his boat <i>Théorème</i>. An act of radical refusal, a process of undoing one by one the ties that attach humans to the world, for Grelet this departure was also inseparable from an ongoing campaign of anti-philosophy. Like François Laruelle's "ordinary man" or Rousseau's "solitary walker," Grelet's solitary sailor is a radical theoretical figure, herald angel of an existential rebellion against the world and against philosophy's world-thought, point zero of an anti-philosophy as rigorous gnosis, and apprentice in the <i>herethics</i> of navigation.<br><br>More than a set of scattered reflections, less than a system of thought, <i>Theory of the Solitary Sailor</i> is a gnostic device. It answers the supposed necessity of realizing the world-thought that is philosophy (or whatever takes its place) with a steadfast and melancholeric refusal. As indifferently serene and implacably violent as the ocean itself, devastating for the sufficiency of the world and the reign of semblance, this is a lived anti-philosophy, a perpetual assault waged from the waters off the coast of Brittany, amid sea and wind.