The Cartesian Other is the counterpart to the Cartesian Self. According to Descartes, there is a divide intrinsic to human consciousness, such that you cannot ever bridge the space between your own consciousness and that of another.

This "other" is in essence theoretical, since one cannot ever be empirically shown such an "other."

Put differently, Descartes concluded cogito ergo sum, "I think, therefore I am," that is, that the presence of a self of which to speak (an "I") proves its existence to oneself; however, according to his Wax Argument, one could never similarly demonstrate the existence of the "other."