"The first thinker to introduce the purely monistic conception of substance into science and appreciate its profound importance was the great philosopher Baruch Spinoza; his chief work appeared shortly before his death in 1677, just one hundred years before Lavoisier gave empirical proof of the constancy of matter by means of the chemist's principle instrument, the balance. In his stately pantheistic system the notion of the world (the universe, or the cosmos) is identical with the all-pervading notion of God; it is at one and the same time the purest and most rational monism and the clearest and most abstract monotheism. This universal substance, this “divine nature of the world,” shows us two different aspects of its being, or two fundamental attributes — matter (indefinitely extended substance) and spirit (the all-embracing energy of thought). All the changes which have since come over the idea of substance are reduced, on a logical analysis, to this supreme thought of Spinoza's; with Goethe I take it to be the loftiest, profoundest, and truest thought of all ages. [Original in German: Der erste Denker, der den reinen monistischen »Substanzbegriff« in die Wissenschaft einführte und seine fundamentale Bedeutung erkannte, war der große Philosoph Baruch Spinoza; sein Hauptwerk erschien kurz nach seinem frühzeitigen Tode, 1677,...]"