"While Herr Bernstein returns to Kant “to a certain point” Herr Stern speaks to us of the old Spinoza, and asks us to return to the philosophy of that great and noble Jewish thinker. That is something else, and far more reasonable than Herr Bernstein's call. Indeed, it is important and interesting to study the question of whether there is something in common between the philosophical ideas of Marx and Engels on the one hand, and Spinoza's on the other. [...] Meanwhile, I assert with full conviction that, in the materialist period of their development, Marx and Engels never abandoned Spinoza's point of view. That conviction, incidentally, is based on Engels's personal testimony. [...] After visiting the Paris World Exhibition in 1889, I went to London to make Engels's acquaintance. For almost a whole week, I had the pleasure of having long talks with him on a variety of practical and theoretical subjects. When, on one occasion, we were discussing philosophy, Engels sharply condemned what Stern had most inaccurately called “naturphilosophische materialism”. “So do you think,” I asked, “old Spinoza was right when he said that thought and extent are nothing but two attributes of one and the same substance?” “Of course,” Engels replied, “old Spinoza was quite right.”"