“Spinoza is the clear and luminous side of Modern philosophy. He is the negation of bourgeois mediation and of all the logical, metaphysical, and juridical fictions that organize its expansion. He is the attempt to determine the continuity of the revolutionary project of humanism. With Spinoza, philosophy succeeds for the first time in negating itself as a science of mediation. In Spinoza there is the sense of a great anticipation of the future centuries; there is the intuition of such a radical truth of future philosophy that it not only keeps him from being flattened onto seventeenth-century thought but also, it often seems, denies any confrontation, any comparison. Really, none of his contemporaries understands him or refutes him.”

This proposition is infinitely important; only, negation as such is formless abstraction. However, speculative philosophy must not be charged with making negation or nothing an ultimate: negation is as little an ultimate for philosophy as reality is for it truth. Of this proposition that determinateness is negation, the unity of Spinoza's substance — or that there is only one substance — is the necessary consequence. Thought and being or extension, the two attributes, namely, which Spinoza had before him, he had of necessity to posit as one in this unity; for as determinate realities they are negations whose infinity is their unity. According to Spinoza's definition, of which more subsequently, the infinity of anything is its affirmation. He grasped them therefore as attributes, that is, as not having a separate existence, a self-subsistent being of their own, but only as sublated, as moments; or rather, since substance in its own self lacks any determination whatever, they are for him not even moments, and the attributes like the modes are distinctions made by an external intellect.
Georg Wilhelm Friedrich Hegel, The Science of Logic, 1812
G - L, Georg Wilhelm Friedrich Hegel

Selected works, The Savage Anomaly: The Power of Spinoza's Metaphysics and Politics (1991)

Part II, Section 21
Principles of Philosophy of the Future http://www.marxists.org/reference/archive/feuerbach/works/future/index.htm (1843)

Lev Vygotsky, in his collected notebooks [original in Russian]
S - Z

Preface
Spinoza's Critique of Religion (1965)

Friedrich Engels, in his The Dialectics of Nature
A - F

Context: For Spinoza, philosophy originates in the very personal... feeling of emptiness that in the philosophical tradition has earned the distinguished name of contemptu mundi, the contempt for worldly things, or, better, vanitas.... Spinoza says that... success in life is just a postponement of failure;... pleasure is just a fleeting respite from pain; and... the objects of our striving are vain illusions....
The feeling of vanitas Spinoza describes is... a dire encounter with the prospect of descent into absolute nothingness, a life without significance coming to a meaningless end.... The experience Spinoza records... establishes... the moment of extreme doubt, fear, and uncertainty that precedes the dawn of revelation.... the journey... is one trodden by poets, philosophers, and theologians too numerous to mention, who for millennia have recorded this feeling that life is a useless passion, a wheel of ceaseless striving, a tale told by an idiot, full of sound and fury, signifying nothing, and so on.<!--pp. 55-56

Matthew Stewart, The Courtier and the Heretic (2006)

Vygotsky [original in Russian]

Will Durant, beginning with a quote of Sir Frederick Pollock in Life and Philosophy of Spinoza (1899)
A - F