"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 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 and spirit . 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."

“Humanam impotentiam in moderandis et coercendis affectibus servitutem voco; homo enim affectibus obnoxius sui juris non est sed fortunæ in cujus potestate ita est ut sæpe coactus sit quanquam meliora sibi videat, deteriora tamen sequi.”

“Meum institutum non est verborum significationem sed rerum naturam explicare”

“Hic conatus aliquid agendi et etiam omittendi ea sola de causa ut hominibus placeamus, vocatur ambitio præsertim quando adeo impense vulgo placere conamur ut cum nostro aut alterius damno quædam agamus vel omittamus; alias humanitas appellari solet.”

“veritas norma sui et falsi est”

“Ordo et connexio idearum idem est ac ordo et connexio rerum”

“[B]y Natura naturans we must understand what is in itself and is conceived through itself, or such attributes of substance as express an eternal and infinite essence, that is … God, insofar as he is considered as a free cause. But by Natura naturata I understand whatever follows from the necessity of God's nature, or from God's attributes, that is, all the modes of God's attributes insofar as they are considered as things which are in God, and can neither be nor be conceived without God.”