Ethics
Spinoza for the 21st Century — a modern reading of the work that dissolved the boundary between God and Nature
How to read Spinoza today
There are books one reads and books one passes through, and Spinoza's Ethics is, beyond doubt, of the second kind. Published only after its author's death, in 1677, it comes down to us as a strange object: a treatise on God, the mind, the passions, and human freedom, written in the rigid form of a geometry textbook, with definitions, axioms, propositions, and demonstrations linked one to the next. At first glance it intimidates. Yet beneath that austere scaffolding throbs one of the most liberating thoughts ever set down on paper — the thesis that to understand the necessity of things is the very form of our being free. This preface exists to lower the book's guard: to explain who the man was who wrote it, why he wrote it in so peculiar a manner, how this edition has been built for you to pass through it without losing your way, and why, in 2026, it is so well worth doing.
You need no training in philosophy to read this edition. You need only the patience to follow a thread that never breaks. Each difficult piece comes accompanied by a translation into the language of today. If at some point the numbering alarms you, ignore it and follow the prose: it was written to lead you, not to test you.
1.The man who ground lenses and refused the world
Baruch de Spinoza — who would later sign in Latin as Benedictus, and whom we might call in Portuguese Bento — was born in Amsterdam in 1632, in the heart of a prosperous community of Sephardic Jews. They were families who had fled the Inquisition in Portugal and Spain and found, in the tolerant Dutch republic, a rare refuge in which to live and pray in peace. The boy grew up speaking Portuguese at home, studying the Torah and the Talmud at the synagogue school, destined, to all appearances, to become a learned pillar of that community. That is not what happened. As he matured, Spinoza began to ask questions no one there wished to hear: about the true authorship of Scripture, about the immortality of the soul, about whether God really had the personal form that tradition ascribed to him.
The reaction was brutal. On 27 July 1656, at only twenty-three years of age, Spinoza received the cherem — the Jewish excommunication — and no ordinary one: the document that expels him is the most violent known in the records of that community. It cursed him by day and by night, in his lying down and in his rising up, and forbade anyone to come near him, to speak with him, to read what he might write, or to stand within four cubits of him. At a single stroke the young man lost family, his mother tongue in daily life, community, and name. Most men would have begged to return. Spinoza did not retreat a hair's breadth — and, according to legend, received the sentence with a serenity that already heralded his philosophy.
What Paul says of Peter tells us more about Paul than about Peter. — attributed to Spinoza, on how we project our passions
What came afterward was one of the most upright lives in the history of philosophy. So as to depend on no patron nor any institution, Spinoza learned a manual trade: grinding lenses for spectacles, microscopes, and telescopes — fine, silent work that suited his search for a clear vision of things. He lived on very little, renting modest rooms in towns around Amsterdam and, at last, in The Hague. He refused a chair at the University of Heidelberg because it came with the implicit condition that he not disturb the established religion — and he would not trade his freedom to think for a post. He likewise refused inheritances and generous pensions, accepting only the strictly necessary. He died young, in 1677, at forty-four years of age, probably of a pulmonary disease aggravated by the glass dust he breathed in grinding lenses. His masterwork, the Ethics, kept back so as not to provoke persecution in his lifetime, was published a few months later by faithful friends — and almost at once condemned and banned. It would take more than a century for the world to begin to understand what it had lost.
2.Why write philosophy as one proves theorems
The first thing that strikes whoever opens the Ethics is its form. There is no essay, no dialogue, no confession. There are definitions, axioms, numbered propositions and, after each one, a demonstration — exactly as in Euclid's Elements, the geometry textbook that for two thousand years was the model of rigorous reasoning. Spinoza called this procedure ordine geometrico: to set forth philosophy "in the manner of the geometers." To the modern reader this may sound like pedantry or coldness. It is the opposite of that.
Behind the choice lies a vertiginous wager on the nature of reality: that the universe is mathematically intelligible. Spinoza believed that everything that exists follows from the nature of things with the same absolute necessity by which the properties of a triangle follow from its definition. No one decides that the interior angles of a triangle sum to two right angles: it simply follows, eternally and inevitably, from what a triangle is. For Spinoza, the whole world is like this. There is no chance, no arbitrary miracle, no God who deliberates and could have done otherwise. There is an order that could not be otherwise — and, for that very reason, an order that can be demonstrated, step by step, without appeal to faith, to authority, or to fear.
To write geometrically is, therefore, a gesture of radical honesty. Rather than asking you to believe, Spinoza commits himself to show. Each assertion must rest upon the preceding ones, before your eyes, as each theorem leans on the axioms. You are never invited to swallow a conclusion; you are invited to verify it. It is also a form of protection against the passions: geometry does not grow heated, does not flatter, does not threaten. To treat of the human emotions — of hatred, of jealousy, of love, of hope — "as though they were lines, planes, and bodies," in the author's celebrated phrase, is the way Spinoza found to look upon our affective life without moralism and without terror, with the calm of one who studies nature rather than judging it.
3.How this book works
This edition neither rewrites Spinoza nor summarizes him: it accompanies him. The original text — his definitions and, above all, his propositions and demonstrations — is all here, translated into the Portuguese of today and carefully set apart, so that you always know when you are hearing the voice of the philosopher himself and when you are being guided by us. To that end we have created a simple visual grammar, repeated across all five parts of the book, which is well worth recognizing from the outset.
Whatever is, is in God; and nothing can be, nor be conceived, without God.
The blocks like the one above, marked with a seal that indicates the part and the exact number (here, Part I · Proposition XV), are the voice of Spinoza: each carries one of the propositions of the Ethics, modernized in language but faithful to the meaning. It is the skeleton of the argument, that which he sets out to prove. When a proposition is especially decisive — a climax of the reasoning — the seal is given an extra emphasis, so that you feel the weight of the moment.
Demonstration Just below many propositions comes the proof, reconstructed in present-day language: the chain of reasons that compels the conclusion. Half the beauty of the Ethics lies precisely here, in how each step locks into the one before, with no slack. Every demonstration closes with the sign that the geometers use to say "it is proved." ∎
And, scattered through the text, these boxes do the work of a translator of ideas: they take the point that has just been demonstrated and say it again, slowly, with examples, undoing misunderstandings before they take hold. When Spinoza says "God," for instance, it is here that we recall that he speaks not of a bearded person who punishes and forgives, but of total reality insofar as it exists through itself. Use these boxes as breathing spaces: whenever a passage seems too abstract, the explanation in plain language will be close at hand.
Between these blocks runs the prose — the guiding thread, in paragraphs like this one. It is the prose that prepares each proposition, stitches one to another, and shows where the argument is heading. You need not memorize the Roman numerals nor master the Latin: it is enough to follow the prose, which never abandons the reader. The small geometric figures that separate the sections are not idle ornament — they are a nod to Spinoza's own method, reminding us, at every turn, that we are constructing a figure, not piling up opinions.
4.Why read Spinoza in 2026
We could read Spinoza merely as a museum piece — a brilliant heretic of the seventeenth century. That would be a waste. Few thinkers have aged so well, and almost none speaks so directly to our present unease. His idea that nature and divinity are one and the same thing, governed by intelligible laws and not by caprice, anticipates by three centuries the worldview of modern science; not by chance do physicists and biologists return to citing him. In a time when we ask what the mind is, whether there is an "I" behind our thoughts, and how it relates to the body, Spinoza offers an answer of disconcerting elegance: mind and body are not two substances at war, but the same reality seen from two angles.
And there is the properly ethical part, which gives the book its name. Spinoza teaches us to regard our emotions not as sins to be fought nor as tyrants to be obeyed, but as natural effects we can understand — and which, once understood, cease to govern us blindly. In an age saturated with manufactured rage, with algorithmic anxiety, and with sad passions sold wholesale, this serenity won by reason sounds almost revolutionary. Freedom, for Spinoza, is not doing what one wishes; it is understanding why one wishes it, and so ceasing to be dragged along. To know necessity is his form of being free.
Finally, we live in the age of machines that reason — systems that deduce, chain inferences, and model the world in formal terms. There is something profoundly current in a philosopher who staked everything on the idea that the real is, at its root, intelligible, deducible, demonstrable. To read the Ethics in 2026 is to find again, at its source, the intuition that drives much of our technology, and to measure how much it still has to teach us about what it means to think with clarity and to live with lucidity. The book you hold in your hands was made for that crossing. Turn the page: the geometry of the world begins in God, that is, in Nature.
“Whatever is, is in God, and nothing can be or be conceived without God.”Proposition XV
God, or Nature
Spinoza opens the Ethics in a manner that disconcerts even today: with numbered definitions, axioms, and propositions, linked together as in a treatise of geometry. This is neither a mathematician's quirk nor gratuitous coldness. Behind the method lies a vertiginous conviction — that the universe is mathematically perfect, that is, that everything which exists follows from the nature of reality with the same rigorous necessity by which the properties of a triangle follow from its definition. Where tradition saw a God who deliberates, chooses, and might have done otherwise, Spinoza sees an order that could not have been otherwise, and which for that very reason can be demonstrated. To write "in the manner of the geometers" (ordine geometrico) is, for him, the only honest way to speak of God: without appeal to faith, to authority, or to fear — only reason upon reason. This book does not dismantle that scaffolding — it translates it into the language of today. You will find the original propositions and demonstrations set apart, with their exact reference, and around them the explanation that makes the argument breathable without betraying it.
Whenever a set-apart block appears with a seal (for example, Part I · Prop. XV), it is the voice of Spinoza himself, modernized but faithful to the sense. The smaller blocks marked Demonstration reconstruct, in present-day language, the proof he gives — for half the beauty of the book lies precisely in how each step rests upon the one before. The running text is the guide. There is no need to memorize the numbering: it is enough to follow the thread, which never breaks.
1.Three words that hold up the universe
Before proving anything at all, Spinoza fixes his vocabulary, and he does so with the parsimony of a geometer who defines his terms before the first theorem. The whole of Part I — and, at bottom, the entire book — rests upon three words. To understand them is already to have traveled half the way. Substance is that which exists in itself and is conceived through itself: something that depends on no other thing, neither to exist nor to be thought. By contrast, a mode is everything that exists in another thing and can be conceived only through it — anything particular and passing: you, this page, a stone, a number, a thought. Between the two stands the attribute, which is each fundamental form through which the intellect apprehends the essence of substance — a face by which the real shows itself. We humans know only two of these faces: Thought and Extension (space, matter); Spinoza insists, however, that substance has infinite attributes, of which these two are the part that concerns us.
Note the hierarchy, for from it everything derives: substance comes first, and the modes are merely its states, like the waves that exist "in" the water without ever being anything other than water in motion. You are not a thing alongside reality; you are a manner in which reality, at a certain point, happens. From this seemingly arid ordering — three definitions and a few axioms — Spinoza will draw, step by step and without ever appealing to anything outside the argument, one of the most radical theses ever written.
2.Why only one substance can exist
The argument now gathers speed, and it is worth following closely, for it is here that the arithmetic of being is decided. Two substances could differ from each other in only two ways: either by their attributes, or by their modes. But the modes are posterior and dependent — set them aside, and only the attribute remains to distinguish; therefore there cannot be two substances with the same attribute, for nothing would remain to separate them, and they would in truth be one and the same. Add to this that a substance, by definition, depends on nothing external: it cannot be produced or caused by anything else, because then it would depend on that thing in order to be conceived, and would cease to be substance. If nothing external produces it, it is cause of itself — and from this follows the first great result:
Existence belongs to the nature of substance: its essence necessarily involves existing.
Demonstration Substance cannot be produced by anything external to itself (for nothing external determines it); it is therefore cause of itself — that is, its own essence implies existing. To say that one clearly understands a substance and still doubts whether it exists would be like having a true idea and suspecting that it might perhaps be false: pure contradiction. ∎
And if substance exists by its own nature, with nothing to limit it from without, then it cannot be partial, cut off, finite — for to be finite is precisely to be limited by another thing of the same kind. Hence the second result, which seems abstract but is the pivot of everything:
Every substance is necessarily infinite.
Now join the pieces that have been locked one into another: substance exists necessarily, is infinite, and there cannot be two with the same attribute. Spinoza then gives a name to that which he had been describing without haste. He calls God the absolutely infinite being — the substance that consists of infinite attributes, each one expressing an eternal and infinite essence. And, in a gesture that scandalized his century, he does not ask you to believe in the existence of this God: he demonstrates it.
God — the substance consisting of infinite attributes, each expressing eternal and infinite essence — necessarily exists.
Demonstration For each thing a reason must be capable of being given, whether for its existing or for its not existing. If God did not exist, there would have to be a cause that prevented him — and that cause would lie either in the nature of God or outside it. Outside it, it would be another substance of another nature, which would have nothing in common with God and therefore could not even touch him. Within his nature, it would be necessary that the very essence of an absolutely perfect being should enclose a contradiction — which is absurd. Since there is no cause, neither internal nor external, that denies his existence, God necessarily exists. ∎
"God," here, is not a person: he has no beard and no voice, he neither punishes nor pardons, he did not choose to create the world on a Tuesday. It is the name Spinoza gives to total reality insofar as it exists by itself, necessary and infinite. Hold on to this strangeness — it is the heart of pantheism, and it is precisely what was lacking for the leap to come.
If God is this infinite and unique substance, the question remains: is anything left outside him? Could there exist a second being, independent, alongside God? The answer closes the first half of Part I and prepares the final blow. Any other substance would have to have some attribute; but all the attributes already belong to God, who is infinite; therefore this "other" substance would share an attribute with God — and we have already seen that this is impossible. Therefore:
Besides God, no substance can be or be conceived.
3.The leap: God is Nature
If only one substance exists, and it is infinite, then — note the inevitability of the step — there is absolutely nothing that stands "outside." There is no God in one place and the universe in another, the creator on one side and the creature on the other. Everything that is — every star, every bacterium, every number, every emotion passing through you now — are modes of this single substance, finite manners in which the infinite expresses itself. It is the conclusion toward which the whole part has, proposition after proposition, been opening the way:
Whatever is, is in God; and nothing can be, or be conceived, without God.
This is the sentence that sealed Spinoza's fame — and that, at the age of twenty-three, cost him the harshest excommunication ever pronounced by his community. In Latin he condenses it into an expression that has become celebrated: Deus sive Natura — "God, that is, Nature." The two words do not name distinct things that happen to coincide; they name the same thing, seen from two angles. It is not that God made nature, as a craftsman shapes a vase and then withdraws from his work. God and Nature are a single infinite process: Natura naturans — substance as the active power that eternally produces itself (naturing Nature) — and Natura naturata — the totality of the modes that follow from that power (natured Nature). The world was not created in some instant of the past; it is being deduced, eternally, from the nature of God, in the same necessary and timeless manner by which from a triangle it follows that its angles sum to two right angles.
The consequences are immense, and will occupy the four parts that follow. If nothing stands outside Nature, then there are no miracles in the proper sense — only laws we do not yet understand. There is no plan laid out for your life by an external will that watches over you — only an infinite web of causes of which you are one knot. And yet, far from impoverishing the world, Spinoza hallows it entirely: if everything is in God, then to bend over a leaf, over a theorem, or over the mind itself ceases to be a profane distraction and becomes a way of knowing the divine. This is why freedom, at the end of the book, will not be defined as escaping this order — an impossible thing — but as understanding it to the point of coinciding with it. To know necessity is the Spinozan way of being free.
The more we understand singular things, the more we understand God. — anticipating Part V
This is as far as this sample wished to take you: from the strange geometric method, which reveals itself to be a wager on the mathematical intelligibility of the real, to the pantheist leap that brought you to this book. If the tone, the density, and the visual serve you, it is in exactly this pattern — proposition, demonstration, and explanation, stitched together by geometric art — that the five complete parts, and the afterword on God, Nature, and the age of artificial intelligence, will be built.
End of the sample
You have read the Preface and Part I.
The complete edition has all five parts, plus the afterword and glossary.
Get the full book →