New York Dada known and controversial across the New York, as well as American in general, art scene. His personality was equally intoxicating as his art; according to Richter, "Duchamp's attitude is that life is a melancholy joke, an indecipherable non-sense, not worth the trouble of investigating. To his superior intelligence the total absurdity of life, the contingent nature of a world denuded of all values, are logical consequences of Descartes' Cogito ergo sum." Most famous amongst the works created by Duchamp in the New York period were his ready-mades, particularly the piece entitled "Fountain". During his time in New York he maintained
Cogito, ergo sum for thought". In other words, "the only claim that is indubitable here is the agent-independent claim that there is cognitive activity present". The objection, as presented by Georg Lichtenberg, is that rather than supposing an entity that is thinking, Descartes should have said: "thinking is occurring." That is, whatever the force of the "cogito", Descartes draws too much from it; the existence of a thinking thing, the reference of the "I," is more than the "cogito" can justify. Friedrich Nietzsche criticized the phrase in that it presupposes that there is an "I", that there is such an activity as "thinking",