...I had just finished my first semester (at the university) and had brought along Spinoza's Ethics to read during that vacation. I was never found without the small book. If we went into the woods, I carried it in the pocket of my rainproof cape; and while the others lolled around under the trees, I would search out a deer lookout, climb up to it, and then become absorbed, alternately, in deductions about the sole substance, and then in the view of sky, mountains, and woods.

He [Spinoza] believes in authority. And, of course, he believed in freedom of thought and expression, whereas Hobbes does not. There is a book on Spinoza written by an American ex-Marxist, called Spinoza and the Rise of Liberalism, on these lines. But Spinoza is not a theorist in whom I am particularly interested, because he is too rationalistic for me. But the Ethics is a wonderful book, and full of deep insights and noble feeling. It is totally unhistorical: the idea of timeless truths about human beings seems suspect to me.

I read Spinoza's Ethics for the first time when I was thirteen years old. Of course at school we studied the Bible – which for me is the ultimate philosophical work. However, reading Spinoza opened up a new dimension for me, which is the reason for my continuing dedication to his works. Spinoza's simple principle 'man thinks' has become an existential mindset for me; my copy of his Ethics has become dog-eared and torn. For years I took it with me on my travels and in hotel rooms or intervals in concerts became absorbed by many of its principles. Spinoza's Ethics is the best training ground for the intellect, above all because Spinoza teaches the radical freedom of thought more completely than any other philosopher. This Spinozan brand of freedom is not a release from discipline into arbitrariness of thought, but an active process. The more one is able to determine one's own thoughts – in fact, causing one's own thoughts, thereby creating one's own experience of reality – the more it is possible to become self-determined, to be truly free.

Between 1854 and 1856, while Bain and Spencer were publishing their first major studies of psychology, George Eliot was immersed in the task of translating Spinoza's Ethics (1677). Before the middle of the nineteenth century, relatively little attention had been given to Spinoza by British philosophers, in part because his geometrical style of metaphysics was antithetical to the spirit of eighteenth-century empiricism, and also because of his unpalatable reputation as an atheist. As Lewes remarked, "the accusation of Spinozism was another name for atheism, and deliberate yielding of the soul to Satan". Although Coleridge had absorbed Spinoza's writing as part of his immersion in Continential metaphysics, and Shelley too had been drawn to his religious radicalism, no one before Eliot's generation championed the philosopher in the way that Goethe had done in Germany. By 1878, however, the philosopher Frederick Pollock was commenting in the journal Mind that "in the Ethics of Spinoza we have one of the most remarkable achievements of constructive philosophic genius ever given to the world." Such keen praise was commonly accepted by this time as being neither eccentric nor misguided. Lewes, who was among the first in Britain to give Spinoza serious critical consideration, believed the Ethics opened "a new era in History." Carlyle's literary executor, J. A. Froude, who grudgingly acknowledged in 1855 that "Spinoza's influence over European thought is too great to be denied or set aside," eventually became another important channel for the dissemination of his ideas. [...] There was, then, an increasingly wide spread recognition in the second half of the nineteenth century that Spinoza was a central figure in modern thought, an opinion few in Britain endorsed before the 1850s.

So I came back to philosophy, but differently; feeling it in myself, and in those I met in talk, a fever of the blood. I had come to it as a boy from wonder at the visible world; to know the causes of things; and to feel the sinews of my mind, as one feels one’s muscles in the palaestra. But now we searched the nature of the universe, and our own souls, more like physicians in time of sickness.

It was not that we were in love with the past. We were of an age to feel the present our own, and to suppose it would never outstrip us. In painting and sculpture and verse, the names we grew passionate over looked to us as big as those of Perikles’ day, and it still half surprises me when I find them unknown to my sons. But we seldom stood to enjoy good work, as one stands before a fine view or a flower, in simple gladness that it is. As we hailed each new artist we grew angry with the former ones, as with false guides we had caught out; we hastened, though we knew not where. To freedom, we said; the sculptors no longer proportioned their forms by the Golden Number of Pythagoras, as Pheidias and Polykleitos did; and art would do great things, we said, now it had cast off its chains.

...Aside from a little Spinoza and Plutarch, I have read nothing since my return, as I am quite occupied by my present work. ...I have read lately some amazing theological things, which I have intermingled with a little of Plutarch and Spinoza. ...Just now, I am reading in the evening, Kant's Critique of Pure Reason, translated by Barni, and I am freshening up my Spinoza. [Original in French: Présentement je lis, le soir, le Critique de la raison pure, de Kant, traduit par Barni et je repasse mon Spinoza.] ...If only I do not make a failure also of Saint-Antoine. I am going to start working on it again in a week, when I have finished with Kant and Hegel. These two great men are helping to stupefy me, and when I leave them I fall with eagerness upon my old and thrice great Spinoza. What genius, how fine a work the Ethics is! [Original in French: Pourvu que je ne rate pas aussi saint Antoine! Je vais m'y remettre dans une huitaine quand j'en aurai fini avec Kant et avec Hegel! Ces deux grands hommes continuent à m'abrutir et, quand je sors de leur compagnie, je tombe avec voracité sur mon vieux et trois fois grand Spinoza! Quel génie! quelle œuvre que l'Éthique!] ...I knew Spinoza's Ethics, but not the Tractatus Theologico-Politicus. The book astounds me; I am dazzled, and transported with admiration. My God, what a man! what an intellect! what learning and what a mind! [Original in French: Je connaissais l'Éthique de Spinoza, mais pas du tout le Tractatus théologico-politicus, lequel m'épate, m'éblouit, me transporte d'admiration. Nom de Dieu, quel homme! quel cerveau! quelle science et quel esprit!]

The Ethics is a book of concepts (the second kind of knowledge), but also of affects (the first kind) and percepts (the third kind) too. Thus the paradox in Spinoza is that he's the most philosophical of philosophers, the purest in some sense, but also the one who more than any other addresses non-philosophers and calls forth the most intense non-philosophical understanding. That is why absolutely anyone can read Spinoza, and be very moved, or see things quite differently afterward, even if they can hardly understand Spinoza's concepts. Conversely, a historian of philosophy who understands only Spinoza's concepts doesn't fully understand him.

It is a curious thing, after years have elapsed, to go back upon the pages of a favourite author. Nothing shows us more forcibly the change that has taken place in ourselves. The book is a mental mirror — the mind starts from its own face, so much freshness, and so much fire has passed away. The colours and the light of youth have gone together. The judgment of the man rarely confirms that of the boy. What was once sweet has become mawkish, and the once exquisite simile appears little more than an ingenious conceit. The sentiment which the heart once beat to applaud has now no answering key-note within, and the real is perpetually militating against the imagined. It is a great triumph to the poet when we return to the volume, and find that our early creed was, after all, the true religion.

Spinoza has long intrigued me, and for years I've wanted to write about this valiant seventeenth-century thinker, so alone in the world—without a family, without a community—who authored books that truly changed the world. He anticipated secularization, the liberal democratic political state, and the rise of natural science, and he paved the way for the Enlightenment. The fact that he was excommunicated by the Jews at the age of twenty-four and censored for the rest of his life by the Christians had always fascinated me, perhaps because of my own iconoclastic proclivities. And this strange sense of kinship with Spinoza was strengthened by the knowledge that Einstein, one of my first heroes, was a Spinozist. When Einstein spoke of God, he spoke of Spinoza's God—a God entirely equivalent to nature, a God that includes all substance, and a God “that doesn't play dice with the universe”—by which he means that everything that happens, without exception, follows the orderly laws of nature.

It was on Spinoza that I worked the most seriously according to the norms of the history of philosophy — but he more than any other gave me the feeling of a gust of air from behind each time you read him, of a witch's broom which he makes you mount. We have not yet begun to understand Spinoza, and I myself no more than others.

Now I am working on an 'Ethics' à la Spinoza. It is designed to establish the highest principles of all philosophy, in which theoretical and practical reason are united. I have become a Spinozist! Don't be astonished. You will soon hear how.

It delights me that the one thinker I approached in my childhood [Spinoza] and almost adored now meets me again, and as the philosopher of psychoanalysis. Think far enough, correctly enough on any point at all, and you hit upon him; you meet him waiting for you, standing ready at the side of the road. (pp. 75-76)

In 1676 Leibniz found a pretext to visit Spinoza in The Hague, having learned that Spinoza was at work on a philosophical treatise of great importance. Spinoza showed Leibniz the manuscript of the 'Ethics', and the two men discussed philosophy together over several days. Although there is no written record of their conversation, it seems likely that these discussions were among the most rewarding in the whole history of philosophy.

I believe we can guess at the first time Einstein read Baruch Spinoza's Ethics (Ethica Ordinae Geometrico Demonstrata), a system constructed on the Euclidean model of deductions from propositions. Soon after getting his first real job at the patent office, Einstein joined with two friends to form a discussion circle, meeting once or twice a week in what they called, with gallows humor, the Akademie Olympia. We know the list of books they read and discussed. High among them, reportedly at Einstein's suggestion, was Spinoza's Ethics, which he read afterwards several times more. Even when his sister Maja joined him in Princeton in later life and was confined to bed by an illness, he thought that reading a good book to her would help, and chose Spinoza's Ethics for that purpose. By that time Spinoza's work and life had long been important to Einstein. He had written an introduction to a biography of Spinoza (by his son-in-law, Rudolf Kayser, 1946); he had contributed to the Spinoza Dictionary (1951); he had referred to Spinoza in many of his letters; and he even had composed a poem in Spinoza's honor. He admired Spinoza for his independence of mind, his deterministic philosophical outlook, his skepticism about organized religion and orthodoxy – which had resulted in his excommunication from his synagogue in 1656 – and even for his ascetic preference, which compelled him to remain in poverty and solitude to live in a sort of spiritual ecstasy, instead of accepting a professorship at the University of Heidelberg.