Who said the following? "I rightly conclude that my essence consists solely in the fact that I am a thinking thing (or substance whose whole essence or nature is to think). And although possibly ... I possess a body with which I am very intimately conjoined, yet because, on the one side, I have a very clear and distinct idea of myself inasmuch as I am only a thinking and unextended thing, and as, on the other, I possess a distinct idea of body, inasmuch as it is only an extended and unthinking thing, it is certain that this I (that is to say, my soul by which I am what I am), is entirely and absolutely distinct from my body, and can exist without it."
René Descartes
George Berkeley
David Hume
Jean-Paul Sartre