Last updated: November 3, 2026

Spinoza’s philosophy rests on one daring idea: there is only one substance, and it can be called either God or Nature, Deus sive Natura. Everything that exists, every rock, thought and person, is a way in which that single substance expresses itself, and everything happens with the same necessity as the properties of a triangle follow from its definition. There is no God outside the world who plans, judges or answers prayers, and there is no free will in the sense of an uncaused choice. Yet Baruch de Spinoza (1632 to 1677) drew from this an ethics of joy rather than despair: we become free, he argued, not by escaping the causes that shape us but by understanding them.

That combination, rigorous determinism with a promise of peace of mind, is why Spinoza appeals to philosophers, physicists and psychologists alike. It is also why he was cursed by his own community, denounced as an atheist across Europe, and later called a “God-intoxicated man” by the poet Novalis. All three descriptions have some truth in them.

The Smartest Person on the Bell Curve

The meme uses the familiar bell curve format, in which the people at both ends of an IQ distribution end up saying something similar while the anxious middle disagrees. On the far left, a relaxed character shrugs: “Religion is just a matter of personal beliefs lol.” In the middle, a sweating priest shouts: “No! Scripture contains the objective and eternal truth of god!” On the far right sits Spinoza, in his famous portrait with long dark curls, explaining that religious conceptions of God are projections of human concerns, passions, morals and imperfections onto the infinite and perfect nature of God.

The caption on the right is a fair paraphrase. In the appendix to the first part of his Ethics, Spinoza argues that people imagine God as a ruler with purposes because they themselves act for purposes, and then interpret storms, earthquakes and diseases as divine anger. In a letter of 1674 he put it more wickedly: if a triangle could speak, it would say that God is eminently triangular, and a circle would say that the divine nature is eminently circular.

But the meme hides a twist that is worth spelling out. In the usual bell curve joke, the genius agrees with the simpleton. Here he does not. Spinoza did not think religion was a matter of personal belief. He thought there was an objective truth about God, and that reason could prove it with geometrical certainty. What he denied was that Scripture was the place to find it. The Bible, he argued, teaches obedience and charity, not metaphysics. So the far right of the curve is closer to the priest’s confidence than to the shrug, only with the authority moved from the book to the argument.

Cursed by Day and Cursed by Night

Baruch de Spinoza was born in Amsterdam in 1632 into a family of Portuguese Jewish merchants, refugees from the Inquisition who had found relative tolerance in the Dutch Republic. On 27 July 1656, when he was twenty-three, the leaders of the Portuguese Jewish congregation pronounced a herem against him, one of the harshest bans in its records. The text survives: cursed be he by day and cursed be he by night, cursed be he when he lies down and cursed be he when he rises up. Nobody was to communicate with him, stay under the same roof or read anything he wrote.

What exactly he had said is not recorded. The herem speaks only of “abominable heresies” and “monstrous deeds”. Historians usually infer the content from his later books and from reports that he had been denying the immortality of the soul, the truth of the Law and any God except, as one report put it, a God who exists only philosophically. He did not appeal. He took the Latin form of his name, Benedictus, and joined circles of freethinking Christians and Cartesians.

He also ground lenses, which is the detail everybody remembers. He was good at it: the scientist Christiaan Huygens admired his lenses, and optics interested him as a science. The romantic image of a starving philosopher grinding glass for bread is exaggerated, since friends supported him and he refused larger gifts, including a professorship at Heidelberg that might have limited his freedom to philosophise. He died in The Hague in 1677, aged forty-four, of a lung disease. It is often said that the glass dust killed him; that is possible, but it is a guess.

In his lifetime he published only a study of Descartes and, anonymously, the Theological-Political Treatise (1670), which argued that Moses did not write the five books attributed to him, that miracles in the sense of breaches of natural law are impossible, and that the purpose of the state is freedom. It was banned, and one critic denounced it as a book forged in hell. His masterpiece, the Ethics, appeared only after his death.

Deus sive Natura: What It Means

The Ethics is written “in geometrical order”, like Euclid: definitions, axioms, propositions, demonstrations, corollaries. Its first part defines substance as that which is in itself and is conceived through itself, needing nothing else in order to exist or be understood. Spinoza then argues that there can be only one such substance, that it must be infinite, and that it is God. Everything else is “in” God, as a mode, a particular modification or state of the one substance.

This substance has infinitely many attributes, but we know only two: thought and extension. A human being is a single mode of substance seen under both attributes at once, a body under extension and a mind under thought. That was Spinoza’s answer to the problem Descartes had left behind, of how an immaterial soul could move a material body. Mind and body do not interact because they are not two things. They are one thing described in two ways, which is why every change in the body has its counterpart in the mind. If you want the problem he was solving, read Descartes’ Philosophical Revolution on Mind-Body Dualism.

The phrase Deus sive Natura, God or Nature, appears in the fourth part of the Ethics, where Spinoza writes that the eternal and infinite being we call God, or Nature, acts from the same necessity by which it exists. Two consequences follow. First, God does not act for purposes, because a being that needs nothing has nothing to aim at; purposes are something we project onto nature. Second, nothing in nature is contingent. Things could not have been produced in any other way or order than they were. Spinoza distinguishes nature as active and productive, natura naturans, from nature as the totality of what is produced, natura naturata, but both are the same reality considered differently.

Was Spinoza an Atheist?

His contemporaries mostly thought so, and they meant it as an accusation. A God who has no will, no purposes, no providence and no interest in being worshipped did not look like God to them. In the 1780s the German “pantheism controversy” broke out when Friedrich Heinrich Jacobi reported that the revered Lessing had confessed to being a Spinozist, and Jacobi argued that Spinozism, consistently thought through, was atheism and fatalism.

The Romantics read him the other way. Novalis called him a God-intoxicated man, and Goethe treasured the Ethics. On their reading Spinoza did not remove God from the world but found God everywhere in it. In 1929, asked by a New York rabbi whether he believed in God, Albert Einstein replied by telegram that he believed in Spinoza’s God, who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with the fates and actions of human beings.

So was he an atheist? If atheism means denying a personal God who creates by choice, rewards, punishes and hears prayers, then Spinoza denied that God as firmly as any atheist. If it means denying that there is anything infinite, necessary and worthy of the deepest love, he was the opposite of an atheist; the word “God” appears on almost every page of the Ethics, and its final part culminates in the intellectual love of God. Scholars still argue whether pantheism is the right label, or whether some things are “in” God without being identical to God. The safest answer is that Spinoza changed the meaning of the question.

The Treatise That Made Him Infamous

During his lifetime Spinoza was notorious not for the Ethics, which appeared only after his death in 1677, but for a book he published anonymously in 1670: the Theological-Political Treatise. It carried a false imprint naming a Hamburg publisher, although it was printed in Amsterdam, and it was soon banned. The book did something that seems ordinary today and was explosive then. It proposed reading the Bible the way a natural scientist studies nature: from the text itself, its language, its history and the circumstances of its authors, rather than from what theologians had decided in advance it must mean.

The results were unsettling. Spinoza argued that Moses could not have written all of the five books traditionally attributed to him, since they describe his death and use place names from later periods. He treated the prophets as people of unusually vivid imagination and moral seriousness, not as sources of philosophical or scientific truth, and he read the miracle stories as reports by people who did not understand natural causes. Scripture, on his account, teaches obedience and charity, not metaphysics, which means that philosophy and theology have different jobs and should leave each other alone. Both Jewish and Christian authorities found that division intolerable, because it took from them the power to decide what reason was allowed to conclude.

The political half of the book draws the conclusion. Since nobody can surrender their judgement to someone else, a state that tries to control thought will produce hypocrites and rebels rather than loyal citizens. The final chapter argues that in a free republic everyone should be allowed to think what they wish and to say what they think, provided they do not act against the laws. It is one of the earliest philosophical defences of freedom of thought, written in a republic that had just seen how fragile its own toleration was.

The treatise made Spinoza famous across Europe, mostly as a dangerous atheist. Yet it also drew visitors. In 1676 the young Gottfried Wilhelm Leibniz, already corresponding with him, came to The Hague and spent several days in conversation with him. Leibniz later played down the meeting and spent years arguing against Spinoza’s necessitarianism, but the encounter between the lens grinder and the courtier remains one of the great conversations of the seventeenth century, all the more fascinating because neither of them left a full account of what was said. We know that Leibniz showed Spinoza a short proof of God’s existence and left with notes on parts of the Ethics and a lifelong problem to solve.

The Stone That Thought It Was Free

If everything follows from the nature of substance with geometrical necessity, then so do your actions. Spinoza accepts this without flinching. In a letter of 1674 he imagines a stone set in motion by an external cause. If the stone could think, he says, it would believe itself completely free and think it continued moving only because it wanted to. That is human freedom as people usually understand it: we are conscious of our desires and ignorant of the causes that determine them. In the Ethics he adds that a baby believes it freely wants milk and a drunk believes he freely says what he later wishes he had kept to himself.

This is not fatalism in the lazy sense. Spinoza does not say that our efforts make no difference; they are among the causes through which things happen. And he keeps a word for freedom, but redefines it. A thing is free, he says, if it exists from the necessity of its own nature and is determined to act by itself alone. Only God is free in the full sense. Human beings become freer to the degree that what they do follows from their own understanding rather than from external pressures they do not grasp. Freedom is not the absence of causes. It is being the adequate cause of what you do.

Critics have asked whether this leaves room for praise and blame. Spinoza thought it left room for something better: understanding. A person who sees that others act from causes they did not choose will be less inclined to hate them, and Spinoza argues that hatred is always a form of sadness that diminishes the one who feels it. Arthur Schopenhauer reached a similar view by another route, as you can read in Man Can Do What He Wants, But He Cannot Want What He Wants.

A Geometry of the Emotions

The third part of the Ethics turns to the emotions, and its preface contains one of Spinoza’s most quoted promises: he will treat human actions and appetites just as if he were dealing with lines, planes and bodies. Moralists before him had mostly ridiculed or condemned the passions. He wanted to understand them.

His starting point is the conatus: each thing, as far as it can by its own power, strives to persevere in its being. In human beings this striving, when we are conscious of it, is desire, and it is our very essence. From desire Spinoza derives two further basic affects. Joy is the passage to a greater power of acting, and sadness the passage to a lesser one. All other emotions are combinations of these three with the ideas of their causes. Love is joy accompanied by the idea of an external cause; hatred is sadness accompanied by the idea of an external cause; hope is an inconstant joy arising from the idea of something future or past whose outcome we doubt, and fear the corresponding sadness. The definitions are compact enough to fit on a card and precise enough to argue with.

This is the point where Spinoza becomes interesting to psychologists. Emotions, on his account, are not intrusions from outside the self but changes in its power, and they are inseparable from ideas, often confused ideas about what caused them. The neuroscientist Antonio Damasio made Spinoza the patron of his work on the feeling brain in Looking for Spinoza (2003), arguing that the philosopher had anticipated the view that emotions are rooted in the body’s regulation of its own life.

Spinoza’s Psychology: Understanding as Therapy

The fourth part of the Ethics is called “Of Human Bondage”, and it describes what happens when we are driven by passions we do not understand: we see the better and follow the worse. The fifth part, “Of Human Freedom”, offers the remedy. Its key proposition is that an affect which is a passion ceases to be a passion as soon as we form a clear and distinct idea of it. Understanding an emotion does not abolish it, but it changes its character. A fear whose causes we grasp is no longer the same fear.

Readers who know cognitive behavioural therapy will hear something familiar. CBT also works by examining the beliefs behind emotional reactions, and its founders acknowledged a debt to the Stoics, whose influence on modern therapy we trace in Philosophy in Psychotherapy. The parallel with Spinoza is real but should not be overstated. He was not writing self-help, his remedies depend on a whole metaphysics, and the clear and distinct ideas he has in mind are ideas of how the emotion follows from the order of nature, not merely corrected beliefs about a situation. Still, the core move is the same: we suffer less from what we understand.

The kinship with Stoicism has often been noted, and it goes deep. Both teach that nature is a rational, necessary order and that peace of mind comes from accepting it. But Spinoza is warmer. He has no ideal of being unmoved; he wants more joy, more power of acting and more love, only of the right objects. If you want to compare the two, start with What Is Stoicism?.

The Free Man Thinks of Nothing Less Than Death

The end of the Ethics introduces its most mysterious idea. The highest kind of knowledge, which Spinoza calls intuitive knowledge, sees particular things as following from the nature of God, “under a species of eternity”. From it arises the intellectual love of God, a joy accompanied by the idea of God as its cause, and it is in this love that our blessedness and freedom consist. Something of the mind, he argues, is eternal, though this is not the personal survival his former congregation believed in, and commentators have argued about what exactly he meant for more than three centuries.

What is clear is the attitude it supports. “A free man thinks of nothing less than of death,” he wrote, “and his wisdom is a meditation not of death but of life.” It is the opposite of the old philosophical habit of preparing to die, and it explains the tone of the whole book. Bertrand Russell, who did not share his metaphysics, called Spinoza the noblest and most lovable of the great philosophers. Hegel said that to be a philosopher one must first be a Spinozist, and his own system, explained in Hegel’s Dialectic Explained, is unthinkable without him.

The Ethics ends with a sentence that applies to its own difficulty: “all things excellent are as difficult as they are rare.” Spinoza never claimed his road to freedom was easy, only that it existed. For a man who lost his family, his community and his name for following an argument, that may be the most convincing evidence that he meant it. For the larger question of what lies behind the world we see, read What Is Metaphysics?.