Cogito ergo sum. The greatest of all Philosophical blunders! As Deleuze and Gvattari wrote, Descartes’s cogito is self-sufficient set of philosophical concepts.
"To start with, the preceding analysis must be confirmed by taking the example of one of the best-known signed philosophical concepts, that of the Cartesian cogito, Descartes's I: a concept of self. This concept has three components- doubting, thinking, and being (although this does not mean that every concept must be triple). The complete statement of the concept qua multiplicity is "I think 'therefore' I am" or, more completely, "Myself who doubts, I think, I am, I am a thinking thing." According to Descartes the cogito is the always-renewed event of thought. The concept condenses at the point I, which passes through all the components and in which I' (doubting), I" (thinking), and I'" (being) coincide. As intensive ordinates the compo- nents are arranged in zones of neighborhood or indiscernibil- ity that produce passages from one to the other and constitute their inseparability. The first zone is between doubting and thinking (myself who doubts, I cannot doubt that I think), and the second is between thinking and being (in order to think it is necessary to be). The components are presented here as verbs, but this is not a rule. It is sufficient that there are variations. In fact, doubt includes moments that are not the species of a genus but the phases of a variation: perceptual, scientific, obsessional doubt (every concept therefore has a phase space, although not in the same way as in science). The same goes for modes of thought-feeling, imagining, having ideas-and also for types of being, thing, or substance-infinite being, finite thinking being, extended being. It is noteworthy that in the last case the concept of self retains only the second phase of being and excludes the rest."
It is not a matter of attacking cogito due to ignorance or desire to voice a superficial opinion, but just a quest about ourselves: can we still apply Descartes way of self-affirmation? According to Deleuze and Gvattari, philosophical concepts are immersed into the plane of immanence. If the plane of Descartes time has changed, all his perfectly designed cogito does not work anymore.