The difficulty begins with the problem that there are several Spinozas with which to reckon, at least four by my count. The first is the accessible Spinoza, the radical religious scholar who dis­agrees with the churches of his time, presents a new conception of God, and proposes a new road to human salvation. Next comes Spinoza as political architect, the thinker who describes the traits of an ideal democratic state populated by responsible, happy citi­zens. The third Spinoza is the least accessible of the set: the philosopher who uses scientific facts, a method of geometric demonstration and intuition to formulate a conception of the universe and the human beings in it. Recognizing these three Spinozas and their web of depen­dencies is enough to suggest how convoluted Spinoza can be. But there is a fourth Spinoza: the protobiologist. This is the biological thinker concealed behind countless propositions, axioms, proofs, lemmas, and scholia. Given that many of the advances on the sci­ence of emotions and feeling are consonant with proposals that Spinoza began to articulate, my second purpose in this book is to connect this least-known Spinoza to some of the corresponding neurobiology of today. But I note, again, that this book is not about Spinoza's philosophy. I do not address Spinoza's thinking outside of the aspects I regard as pertinent to biology. The goal is more modest. One of the values of philosophy is that throughout its history it has prefigured science. In turn, I believe, science is well served by recognizing that historical effort.

Some of Spinoza's ideas are part and parcel of our culture, but to the best of my knowledge Spinoza is absent as a reference from the modern efforts to understand the biology of the mind. This ab­sence is interesting in itself. Spinoza is a thinker far more famous than known. Sometimes Spinoza appears to rise out of nothing, in solitary and unexplained splendor, although the impression is false—in spite of his originality he is very much a part of his intellectual times. And he appears to dissolve as abruptly, without succession—another false impression given that the essence of some of his forbidden proposals can be found behind the Enlight­enment and well beyond in the century that followed his death.

Nevertheless, when it is your lot to have to endure something that is (or seems to you) worse than the ordinary lot of mankind, Spinoza's principle of thinking about the whole, or at any rate about larger matters than your own grief, is a useful one. There are even times when it is comforting to reflect that human life, with all that is contains of evil and suffering, is an infinitesimal part of the life of the universe. Such reflections may not suffice to constitute a religion, but in a painful world they are a help towards sanity and an antidote to the paralysis of utter despair. - about Spinoza

Such was Benedict Spinoza — thus he lived and thought. A brave and simple man, earnestly meditating on the deepest subjects that can occupy the human race, he produced a system which will ever remain as one of the most astounding efforts of abstract speculation — a system that has been decried, for nearly two centuries, as the most iniquitous and blasphemous of human invention ; and which has now, within the last sixty years, become the acknowledged parent of a whole nation's philosophy, ranking among its admirers some of the most pious and illustrious intellects of the age. The ribald Atheist turns out, on nearer acquaintance, to be a "God-intoxicated man." The blasphemous Jew becomes a pious, virtuous, and creative thinker. The dissolute heretic becomes a child-like, simple, self-denying and heroic man. We look into his works with calm earnestness, and read there another curious page of human history : the majestic struggle with the mysteries of existence has failed, as it always must fail ; but the struggle demands our warmest admiration, and the man our ardent sympathy. Spinoza stands out from the dim past like a tall beacon, whose shadow is thrown athwart the sea, and whose light will serve to warn the wanderers from the shoals and rocks on which hundreds of their brethren have perished.

...If we had the time we should now go on to present the ingenious theory of organism with which Spinoza focused the general ontological scheme specifically on the biological sphere, where mentality is ordinarily seen to be conjoined to physical fact, and particularly on the case of man. It must be enough to say that Spinoza makes it beautifully intelligible from his general premises that the quality and power of a mind are proportionate to the complexity of the body to which it corresponds, so that the perfection of the human body as a piece of physical organization is a direct yardstick for the perfection of the human mind which, as it were, conformally (or: isomorphously) duplicates the body's physical performance on the plane of thought.

As regards the philosophy of Spinoza, it is very simple, and on the whole easy to comprehend; the difficulty which it presents is due partly to the limitations of the method in which Spinoza presents his thoughts, and partly to his narrow range of ideas, which causes him in an unsatisfactory way to pass over important points of view and cardinal questions. Spinoza's system is that of Descartes made objective in the form of absolute truth. The simple thought of Spinoza's idealism is this: The true is simply and solely the one substance, whose attributes are thought and extension or nature: and only this absolute unity is reality, it alone is God. It is, as with Descartes, the unity of thought and Being, or that which contains the Notion of its existence in itself. The Cartesian substance, as Idea, has certainly Being included in its Notion; but it is only Being as abstract, not as real Being or as extension (supra, p. 241). With Descartes corporeality and the thinking 'I' are altogether independent Beings; this independence of the two extremes is done away with in Spinozism by their becoming moments of the one absolute Being. This expression signifies that Being must be grasped as the unity of opposites; the chief consideration is not to let slip the opposition and set it aside, but to reconcile and resolve it. Since then it is thought and Being, and no longer the abstractions of the finite and infinite, or of limit and the unlimited, that form the opposition (supra, p. 161), Being is here more definitely regarded as extension; for in its abstraction it would be really only that return into itself, that simple equality with itself, which constitutes thought (supra, p. 229). The pure thought of Spinoza is therefore not the simple universal of Plato, for it has likewise come to know the absolute opposition of Notion and Being.

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.

For Spinoza, obviously, the human mind, as well as the human body, are individuals (actually, they are the same individual). However, this individuality of the human mind would be threatened if the human mind were made up of ideas whose contents were relatively disparate, if these ideas were not all focused around a particular unified thing, such as the human body.

Spinoza's ethics has nothing to do with a morality; he conceives it as an ethology, that is, as a composition of fast and slow speeds, of capacities for affecting and being affected on this plane of immanence. That is why Spinoza calls out to us in the way he does: you do not know beforehand what good or bad you are capable of; you do not know beforehand what a body or a mind can do, in a given encounter, a given arrangement, a given combination.

Writers, poets, musicians, filmmakers – painters too, even chance reader – may find that they are Spinozists; indeed, such a thing is more likely for them than for professional philosophers. It is a matter of one's practical conception of the “plan”. It is not that one may be a Spinozist without knowing it. Rather, there is a strange privilege that Spinoza enjoys something that seems to have been accomplished by him and no one else. He is a philosopher who commands an extraordinary conceptual apparatus, one that is highly developed, systematic, and scholarly; and yet he is the quintessential object of an immediate, unprepared encounter, such that a nonphilosopher, or even someone without any formal education, can receive a sudden illumination from him, a “flash”. Then it is as if one discovers that one is a Spinozist; one arrives in the middle of Spinoza, one is sucked up, drawn into the system or the composition. (…) What is unique about Spinoza is that he, the most philosophic of philosophers (…) teaches the philosopher how to become a non-philosopher.

Spinoza's ethical views are inextricably intertwined with his metaphysics, and it may be doubted whether his metaphysics is as good as is supposed by followers of Hegel. But the general attitude towards life and the world which he inculcates does not depend for its validity upon a system of metaphysics. He believes that all human ills are to be cured by knowledge and understanding; that only ignorance of what is best makes men think their interests conflicting, since the highest good is knowledge, which can be shared by all. But knowledge, as he conceives it, is not mere knowledge as it comes to most people; it is “intellectual love,” something coloured by emotion through and through. This conception is the key to all his valuations.

[Spinoza] this pure soul, this great realist, the first human being to attempt to become a citizen of the world. . . this down-to-earth passion.

In Spinoza, at the origin of the Modern world, metaphysical theory and the theory of science are given in complete agreement for the first time. They represent the alternative to the entire subsequent path of metaphysics and of the bourgeois theory of science. Spinoza lives as an alternative: Today this alternative is real. The Spinozian analytic of full space and open time are becoming an ethics of liberation in all the dimensions that this discourse constructs and makes available.

Like Socrates, Spinoza avers that blessedness comes only from a certain kind of knowledge—specifically, the "knowledge of the union that the mind has with the whole of Nature."
...the life of contemplation is also a life within a certain type of community—specifically, a fellowship of the mind. Like Socrates with his circle of debating partners, or Epicurus in his garden with his intellectual companions, Spinoza imagines a philosophical future... upon achieving blessedness for himself, he announces in his first treatise, his first step is "to form a society... so that as many as possible may attain it as easily and as surely as possible." For, "the highest good," he claims, is to achieve salvation together with other individuals "if possible."