"This sets us off on a path which was opened for us almost without our knowledge, I think, for we have not really considered it, by two philosophers in history: Spinoza and Marx. Against what should really be called the latent dogmatic empiricism of Cartesian idealism, Spinoza warned us that the object of knowledge or essence was in itself absolutely distinct and different from the real object, for, to repeat his famous aphorism, the two objects must not be confused: the idea of the circle, which is the object of knowledge must not be confused with the circle, which is the real object. In the third chapter of the 1857 Introduction, Marx took up this principle as forcefully as possible. Marx rejected the Hegelian confusion which identifies the real object with the object of knowledge, the real process with the knowledge process: ‘Hegel fell into the illusion of conceiving the real (das Reale) as the result of thought recapitulating itself within itself deepening itself within itself and moving itself from within itself whereas the method that allows one to rise from the abstract to the concrete is merely the mode (die Art) of thought which appropriates the concrete and reproduces (reproduzieren) it as a spiritual concrete (geistig Konkretes)’ (Grundrisse der Kritik der Politischen Ökonomie, Berlin 1953, p. 22). This confusion, which in Hegel takes the form of an absolute idealism of history, is in principle simply a variant of the confusion which characterizes the problematic of empiricism."