Levin again: “Since, for Descartes, the senses are nothing but a source of deception and the body is nothing but perishable matter - that is to say, they are challenges, in both cases, to the power of the ego cogitans , the ego must ‘abandon’ them; the Cartesian ego is a cogito which has dissociated, split off, from its embodiment and taken itself as the object of its ‘love.’ In order to possess absolute certainty and security, Descartes undergoes a process of separation and withdrawal, methodically abandoning all the ‘objects’ of the body’s desires and taking himself, as purely thinking substance, for ‘object.’ This is the narcissistic process, homologous to the process clinically recognized as the defensive comportment of severe depression.  In the isolation of human beings from each other and the separation of human beings from Being, there is indeed cause for deep depression.  Without astonishing prescience, Nietzsche could already see the depression and interpret it as a signifier or nihilism.”