History of Philosophy
From the pre-Socratics asking what the world is made of, to the moderns asking how we can know anything at all.
Why Start Here
Philosophy is the source code. Before physics, before economics, before cognitive science — there were people sitting around asking the most basic questions and refusing to accept bad answers. I wanted to trace the lineage: who built on whom, what problems recurred, what got resolved and what didn’t.
The Pre-Socratics (600–400 BCE)
The first move was surprisingly scientific: what is the world fundamentally made of?
- Thales — water is the substrate of everything. Wrong, but the type of question was new.
- Heraclitus — everything is in flux. “You cannot step into the same river twice.” Change is the fundamental reality.
- Parmenides — the opposite: change is an illusion. Being is one, static, unchanging. Logic over perception.
- Democritus — atoms and void. Everything is made of indivisible particles moving through empty space. Astonishing guess that took 2,300 years to confirm.
The pre-Socratics were trying to do physics without mathematics. The tools weren’t there yet, but the instinct was right.
Socrates, Plato, Aristotle (470–322 BCE)
The canonical sequence. Each one a reaction to the last.
Socrates left no writing. We know him through Plato. His method: ask someone what they mean, then ask again, until the concept either holds or falls apart. He claimed to know nothing — the “Socratic irony.” Executed for corrupting the youth and impiety. The charges were political.
Plato answered the pre-Socratic problem by splitting reality in two. The physical world is a shadow of the real world — the realm of Forms. The Form of a chair is more real than any actual chair. Mathematics pointed at this: the number 3 exists without any three physical objects. His political philosophy (Republic) is deeply authoritarian: rule by philosopher-kings who’ve seen the Forms. Disturbing and brilliant.
Aristotle was Plato’s student and rejected the two-world theory. Reality is here. He built the first systematic logic (syllogisms), categorized biology, ethics, politics, rhetoric, and aesthetics. His framework dominated Western thought for 1,500 years — so thoroughly that medieval thinkers called him simply “the Philosopher.”
The Hellenistic Schools (300 BCE – 200 CE)
After Alexander’s conquests, Greek culture spread. Philosophy turned inward — less about what the world is, more about how to live in it.
- Stoics (Zeno, later Epictetus, Marcus Aurelius) — distinguish what’s in your control (your judgments, desires, actions) from what isn’t (everything else). Virtue is the only good. Marcus Aurelius wrote Meditations as private notes to himself, never meant for publication.
- Epicureans — pleasure is good, but misunderstood. The highest pleasure is ataraxia: tranquility, absence of anxiety. Simple food, friendship, philosophical conversation. Not hedonism.
- Skeptics — suspend judgment on everything you can’t be certain of. Equipoise. Don’t commit.
Medieval Philosophy (400–1400 CE)
Philosophy became theology’s servant — ancilla theologiae. The project was reconciling Greek philosophy with Christian doctrine.
Augustine fused Platonism with Christianity. The Forms became God’s ideas. Evil is absence of good, not a substance.
Aquinas did the same with Aristotle. His Summa Theologica is a systematic attempt to prove everything the Church believed using Aristotelian logic. Five proofs for God’s existence. Infuriatingly careful thinker.
Anselm offered the ontological argument: God is the greatest conceivable being. A being that exists in reality is greater than one that exists only in the mind. Therefore God exists. Kant would later destroy this, but it keeps coming back.
The Early Moderns (1600–1800)
The Scientific Revolution broke the grip of Aristotle and forced a reset.
Descartes — clear the ground entirely. What can I be certain of? The external world might be an illusion. My own existence cannot be doubted while I’m doubting it. Cogito ergo sum. Now rebuild from there. He got stuck trying to prove the external world exists and God isn’t deceiving him. The project was more interesting as a problem than as a solution.
Spinoza — there is only one substance: God, or Nature (same thing). Everything — minds, bodies, emotions — are modes of this single infinite substance. A pantheist system of breathtaking scope written in geometric proof form. Excommunicated by his own Jewish community at 23.
Leibniz — reality is made of windowless monads, each reflecting the universe from its own perspective, pre-harmonized by God. Stranger than it sounds. Also invented calculus independently of Newton.
Locke — empiricism. The mind starts as a blank slate (tabula rasa). All knowledge comes from experience. Led directly to his political philosophy: natural rights, government by consent, right of revolution. Jefferson read Locke closely.
Hume — empiricism pushed further, until it collapses. Causation isn’t observable — you see sequence, not necessity. The self isn’t observable either — you find only a bundle of perceptions. Induction can’t be justified. He woke Kant from his “dogmatic slumber.”
Kant — the synthesis. Yes, all knowledge starts with experience (Hume). But the mind structures experience using categories (space, time, causality) that aren’t derived from it. We can never know things as they are in themselves (Ding an sich) — only as they appear through our cognitive apparatus. Morality: act only on maxims you could will to be universal laws (categorical imperative). One of the hardest thinkers to read. Possibly the most important.
The 19th Century
Hegel — history is the unfolding of Geist (mind/spirit) toward self-knowledge. Everything develops through thesis → antithesis → synthesis. Reality is a process, not a static structure. Dense, controversial, enormously influential.
Marx — took Hegel’s dialectic and flipped it: material conditions drive history, not ideas. The base (economics, production) shapes the superstructure (law, religion, philosophy). Ideology is rationalization of class interest.
Nietzsche — God is dead, and we killed him. The values built on that foundation need replacing. Will to power. The eternal recurrence as a thought experiment: could you affirm your life if you had to live it exactly this way, infinitely? The Übermensch as a figure who creates values rather than inheriting them. Wildly misread — the Nazis removed the anti-nationalism and anti-antisemitism and used the husk.
Mill — utilitarianism refined. Greatest happiness for the greatest number. On Liberty: individual freedom should only be limited to prevent harm to others. Feminist; wrote The Subjection of Women in 1869.
The 20th Century
The English-language tradition (analytic philosophy) and the European tradition (continental philosophy) diverged almost completely.
Analytic: Frege, Russell, Wittgenstein — logic and language. The early Wittgenstein (Tractatus): the limits of my language are the limits of my world. The later Wittgenstein (Investigations): meaning is use. Philosophical problems are often grammatical confusions. Dissolve them, don’t solve them.
Continental: Husserl’s phenomenology (back to lived experience), Heidegger’s Being and Time (what does it mean to exist?), Sartre’s existentialism (existence precedes essence — there’s no given human nature, only choices), Camus (the absurd: life has no inherent meaning, but we should live as if it does anyway).
Later: Rawls’ A Theory of Justice (1971) revived political philosophy. The veil of ignorance: design a just society without knowing what position you’ll occupy in it. Foucault on power and knowledge. Wollstonecraft, Beauvoir on gender.
What’s Landing
The problems don’t get solved — they get inherited. Every generation finds Hume’s problem of induction, Descartes’ problem of other minds, the question of free will, the gap between is and ought. What changes is the vocabulary and the rigor.
The pre-Socratics were doing physics with their bare hands. The medieval thinkers were doing philosophy with one hand tied by orthodoxy. The moderns got rigorous. The 20th century got technical. The problems are the same.
Philosophy looks useless until you notice that it’s the substrate of every other discipline’s assumptions. The physicist who thinks carefully about what “causation” means is doing philosophy. The economist who thinks about utility is doing philosophy. The programmer who thinks about what it means for a program to be “correct” is doing philosophy.
Worth knowing where the substrate came from.