Philosophy Timeline: Understanding the Human Mind

I'm fascinated by philosophy, psychology and the study of the human mind: what we do, and why we do it. This timeline follows 25 thinkers across 2,500 years, from Socrates to Martha Nussbaum.

In short: Many great philosophical traditions took shape between the 6th and 4th centuries BCE, with Confucius in China, the Buddha in India and Socrates, Plato and Aristotle in Greece. This timeline follows 25 thinkers through six eras to today, each with dates, school and a one-line answer to why humans do what they do.

When did the great philosophers live?

Figure: the lifespans of 25 philosophers as bars on a time axis from 600 BCE to today, with a break between 450 CE and 1100 CE. Ancient: Confucius 551–479 BCE, the Buddha c. 563–483 BCE (traditional dates), Socrates c. 470–399 BCE, Plato c. 428–348 BCE, Aristotle 384–322 BCE, Augustine 354–430 CE. Medieval: Ibn Rushd 1126–1198, Thomas Aquinas 1225–1274. Early modern: Descartes 1596–1650, Spinoza 1632–1677, Locke 1632–1704, Hume 1711–1776, Kant 1724–1804. 19th century: Hegel 1770–1831, Kierkegaard 1813–1855, Marx 1818–1883, Nietzsche 1844–1900. 20th century: Freud 1856–1939, Wittgenstein 1889–1951, Heidegger 1889–1976, Sartre 1905–1980, de Beauvoir 1908–1986, Foucault 1926–1984. Contemporary: Dennett 1942–2024, Nussbaum born 1947.

Two bursts, one long gap. Each bar is one life; hover or tap for dates, click to jump to the card. The axis is broken between 450 and 1100 CE, a stretch this list skips. Ancient dates are approximate.
Read more: the six eras at a glance

The 25 thinkers on this page fall into six eras. The list is personal, not a complete canon: it follows the thinkers who shaped how I think about human behavior.

Era Years Key figures Central theme
Ancient 6th century BCE to 6th century CE Socrates, Plato, Aristotle, Confucius, the Buddha, Augustine Foundations of human inquiry: virtue, knowledge, suffering, love
Medieval 5th to 15th century Thomas Aquinas, Ibn Rushd (Averroes) Synthesis of faith and reason
Renaissance and early modern 15th to 18th century Descartes, Spinoza, Locke, Hume, Kant Rationalism versus empiricism; foundations of modern thought
19th century 1800 to 1900 Hegel, Kierkegaard, Marx, Nietzsche Individual existence, social conditions, will to power
20th century 1900 to 2000 Freud, Wittgenstein, Heidegger, Sartre, de Beauvoir, Foucault The unconscious, existentialism, language, power
Contemporary 2000 to present Daniel Dennett, Martha Nussbaum Consciousness, capabilities, emotions

Some lives overlap in surprising ways. Spinoza and Locke were both born in 1632. Wittgenstein and Heidegger were both born in 1889, a few months apart. Confucius, the Buddha (on the traditional dates) and Socrates’ early years fall within roughly a century of each other, in China, India and Greece.

The Buddha’s dates are uncertain. The traditional dates are c. 563–483 BCE; many scholars now place his life later, around 480–400 BCE. The chart uses the traditional dates.

What drives human behavior? Six answers from 2,500 years

Figure: the 25 philosophers grouped by their answer to "why do we do what we do?". Reason and knowledge: Socrates, Ibn Rushd, Thomas Aquinas, Descartes, Kant. Desire and emotion: the Buddha, Augustine, Spinoza, Hume, Nussbaum. Virtue, habit and upbringing: Confucius, Aristotle, Locke. Inner drives: Plato, Nietzsche, Freud, Dennett. Society, history and power: Hegel, Marx, Wittgenstein, de Beauvoir, Foucault. Freedom and anxiety: Kierkegaard, Heidegger, Sartre.

The same question, six kinds of answer. Pick an answer to see who gave it, then tap a face to read their card. The grouping is my own reading of each thinker's one-line answer below.
Read more: how the six answers differ

Every thinker on this timeline answers the question “why do we do what we do?” differently, but the answers cluster into six families. This grouping is my interpretation, based on the one-line summaries in the cards below; most philosophers touch several families.

  1. Reason and knowledge (Socrates, Ibn Rushd, Aquinas, Descartes, Kant): we act on what we know or believe to be right, so bad action comes from ignorance, unclear thinking or failing to follow reason and duty.
  2. Desire and emotion (the Buddha, Augustine, Spinoza, Hume, Nussbaum): feeling comes first. Hume put it most sharply: we act more from passion and habit than from reason.
  3. Virtue, habit and upbringing (Confucius, Aristotle, Locke): character is built by practice, ritual, relationships and education, so better habits and environments make better people.
  4. Inner drives (Plato, Nietzsche, Freud, Dennett): forces inside us that we don’t fully see, from Plato’s divided soul to Freud’s unconscious to Dennett’s competing neural narratives.
  5. Society, history and power (Hegel, Marx, Wittgenstein, de Beauvoir, Foucault): we are shaped by the historical moment, economic conditions, language and the power structures we absorb.
  6. Freedom and anxiety (Kierkegaard, Heidegger, Sartre): we are free and that freedom frightens us, so much of what we do is an escape from it.

The philosophers, one by one

Ancient philosophy 6th century BCE to 6th century CE

Marble bust of Socrates with a broad nose and curly beard, a Roman copy in the Louvre

Socrates

c. 470–399 BCE Classical Greek

“The unexamined life is not worth living” (as reported in Plato’s Apology). Pioneered the method of questioning to understand human nature and ethics.

Why we do what we do: People act wrongly due to ignorance; if we truly know what is good, we will do good.
In the essay: why we do what we do →
Marble portrait head of Plato with a full beard, a Roman copy after Silanion in the Capitoline Museums

Plato

c. 428–348 BCE Classical Greek

Explored the nature of reality, knowledge, and the ideal state. Created the theory of Forms and examined the soul’s structure.

Why we do what we do: Human behavior stems from the conflict between reason, spirit, and appetite within the soul.
In the essay: why we do what we do →
Marble bust of Aristotle with a short curly beard, a Roman copy after Lysippos

Aristotle

384–322 BCE Classical Greek

Systematized logic, ethics, and politics. Studied human flourishing (eudaimonia) and virtue ethics.

Why we do what we do: We act to achieve happiness through virtue, which is developed through habit and practice.
In the essay: why we do what we do →
Faded Han-dynasty tomb fresco showing Confucius in profile

Confucius

551–479 BCE Chinese Philosophy

Emphasized moral cultivation, social harmony, and the importance of relationships and ritual.

Why we do what we do: Human behavior should be guided by virtue, respect for others, and social responsibility.
Sandstone sculpture of the seated Buddha from Sarnath, hands in the teaching gesture

Buddha (Siddhartha Gautama)

c. 563–483 BCE (traditional) Buddhist Philosophy

Explored suffering, desire, and the path to enlightenment through understanding the mind. Many scholars now place his life later, around 480–400 BCE.

Why we do what we do: We act from attachment and desire, which causes suffering; liberation comes through mindfulness.
Painting of Saint Augustine in bishop’s robes holding a quill, by Philippe de Champaigne

Augustine of Hippo

354–430 CE Christian Philosophy

Integrated Christian theology with philosophy, exploring free will, time, and human nature.

Why we do what we do: Human actions are driven by love: either love of God (good) or love of self (sin).
In the essay: why we do what we do →

Medieval philosophy 5th to 15th century

Fresco detail of Averroes in a white turban, from Andrea di Bonaiuto’s Triumph of Saint Thomas Aquinas

Ibn Rushd (Averroes)

1126–1198 Islamic Philosophy

Defended philosophy against religious orthodoxy, emphasizing reason and individual thought.

Why we do what we do: Human behavior should be guided by reason, which can lead to truth and happiness.
Detail of Carlo Crivelli’s painting of Thomas Aquinas in a Dominican habit

Thomas Aquinas

1225–1274 Scholasticism

Synthesized Aristotelian philosophy with Christian doctrine, exploring reason and faith.

Why we do what we do: We act according to our nature, seeking the ultimate good (God) through reason and virtue.
In the essay: why we do what we do →

Renaissance and early modern 15th to 18th century

Portrait of René Descartes with shoulder-length dark hair and a white collar, after Frans Hals

René Descartes

1596–1650 Rationalism

“I think, therefore I am.” Established the foundation of modern philosophy through methodical doubt.

Why we do what we do: We act based on clear and distinct ideas; error comes from hasty judgment and unclear thinking.
In the essay: why we do what we do →
Portrait of Baruch Spinoza with long dark curly hair and a white collar

Baruch Spinoza

1632–1677 Rationalism

Developed a deterministic view of reality where everything follows natural laws, including human emotions.

Why we do what we do: We are driven by emotions and desires; freedom comes from understanding our nature and emotions.
Portrait of John Locke with long grey hair, by Godfrey Kneller

John Locke

1632–1704 Empiricism

Argued that knowledge comes from experience; the mind is a “blank slate” shaped by sensory input.

Why we do what we do: Our behavior is shaped by experience and education; we can be improved through better environments.
Portrait of David Hume in a red coat, by Allan Ramsay

David Hume

1711–1776 Empiricism

Skeptical about reason’s power; emphasized the role of habit, custom, and sentiment in human nature.

Why we do what we do: We act more from passion and habit than reason; moral judgments come from feelings, not logic.
In the essay: why we do what we do →
Portrait of Immanuel Kant in a brown coat, by Johann Gottlieb Becker

Immanuel Kant

1724–1804 German Idealism

Synthesized rationalism and empiricism; developed the categorical imperative for moral action.

Why we do what we do: We should act from duty and universal moral laws, not just desire or consequence.
In the essay: why we do what we do →

19th-century philosophy 1800 to 1900

Portrait of an elderly Hegel in a fur collar, by Jakob Schlesinger, 1831

Georg Wilhelm Friedrich Hegel

1770–1831 German Idealism

Developed the dialectical method; saw history as the progressive unfolding of absolute spirit.

Why we do what we do: We act within historical contexts; consciousness develops through conflict and resolution.
Pencil sketch of a young Søren Kierkegaard with wavy hair

Søren Kierkegaard

1813–1855 Existentialism

Emphasized individual existence, choice, and the leap of faith; critiqued systematic philosophy.

Why we do what we do: We act from anxiety about our freedom; authentic existence requires passionate commitment.
In the essay: why we do what we do →
Black-and-white photograph of Karl Marx with a full white beard, 1875

Karl Marx

1818–1883 Historical Materialism

Analyzed capitalism and class struggle; argued that material conditions shape consciousness.

Why we do what we do: Our actions are determined by economic and social conditions; consciousness follows material reality.
In the essay: why we do what we do →
Black-and-white photograph of Friedrich Nietzsche with a large moustache

Friedrich Nietzsche

1844–1900 Existentialism

“God is dead.” Challenged traditional morality and advocated for creating one’s own values.

Why we do what we do: We act from will to power; we must create our own meaning in a meaningless universe.
In the essay: why we do what we do →

20th-century philosophy 1900 to 2000

Black-and-white photograph of Sigmund Freud holding a cigar, by Max Halberstadt

Sigmund Freud

1856–1939 Psychoanalysis

Explored the unconscious mind, revealing hidden motivations behind human behavior.

Why we do what we do: Much of our behavior is driven by unconscious desires, fears, and childhood experiences.
Black-and-white photograph of Ludwig Wittgenstein in a tweed jacket, 1929

Ludwig Wittgenstein

1889–1951 Analytic Philosophy

“The limits of my language mean the limits of my world.” Explored language and its role in thought.

Why we do what we do: Our actions are shaped by language games and forms of life that give meaning to our words.
Black-and-white photograph of an older Martin Heidegger giving a lecture

Martin Heidegger

1889–1976 Existentialism

Explored the question of Being; emphasized authenticity and being-toward-death.

Why we do what we do: We act to flee from anxiety about our mortality; authentic existence requires facing this anxiety.
Black-and-white photograph of Jean-Paul Sartre in thick glasses, 1965

Jean-Paul Sartre

1905–1980 Existentialism

“Existence precedes essence.” We are condemned to be free and must create our own meaning.

Why we do what we do: We act to escape the overwhelming responsibility of absolute freedom, often in bad faith.
In the essay: why we do what we do →
Black-and-white photograph of Simone de Beauvoir smiling, wearing a headscarf

Simone de Beauvoir

1908–1986 Feminist Existentialism

“One is not born, but rather becomes, a woman.” Examined how social conditioning shapes identity.

Why we do what we do: Our behavior is heavily influenced by social expectations and power structures we internalize.
In the essay: why we do what we do →
Black-and-white photograph of Michel Foucault in glasses and a dark suit

Michel Foucault

1926–1984 Post-Structuralism

Analyzed how power shapes knowledge, identity, and behavior through institutions and discourse.

Why we do what we do: Our actions are shaped by invisible power structures operating through knowledge systems.

Contemporary philosophy 2000 to present

Colour photograph of Daniel Dennett with a white beard and glasses

Daniel Dennett

1942–2024 Philosophy of Mind

Applied evolutionary and computational approaches to consciousness and free will.

Why we do what we do: Our behavior emerges from complex neural processes; consciousness is multiple competing narratives.
Colour photograph of Martha Nussbaum smiling, 2010

Martha Nussbaum

born 1947 Capabilities Approach

Bridges ancient philosophy with contemporary issues, emphasizing human capabilities and emotions.

Why we do what we do: We act to develop our human capabilities; emotions play a crucial role in moral reasoning.

Quiz: who thought this?

Quiz: the page shows one philosopher's answer to "why do we do what we do?" and four portraits; pick the thinker who gave it. For example, "We act more from passion and habit than reason" is David Hume, and "We act from will to power" is Friedrich Nietzsche. The quiz needs JavaScript; every answer is in the cards above.

Ten rounds, four faces each. Every answer comes from the cards above, so a wrong guess is a good excuse to read one.

Timeless questions about human nature

My research notes

Featured: Why Do We Do What We Do? A Philosophical Journey Across the Ages. I wrote a longer exploration of human motivation through the lens of philosophy, tracing how thinkers from ancient Greece to modern neuroscience have answered this question. It connects the insights on this timeline with modern psychology and neuroscience.

Research connections I still want to explore:

AI credit: this exploration was developed with help from AI research assistants. They helped synthesize and phrase ideas; the perspectives and critical analysis are my own.

Portrait credits

Read more: where the 25 portraits come from

All portraits come from Wikimedia Commons and are either in the public domain or under a Creative Commons license. I cropped and resized them; Creative Commons BY-SA images remain under the same license. Portraits of ancient thinkers are later artistic depictions, not likenesses.

Frequently asked questions

Who is considered the father of Western philosophy?

Socrates (c. 470–399 BCE) is usually called the father of Western philosophy, because his habit of questioning people about justice, courage and the good life set the pattern for later ethics. He wrote nothing himself; almost everything we know about him comes from his students Plato and Xenophon. Thales of Miletus, a century earlier, is often called the first Greek philosopher.

What is the difference between rationalism and empiricism?

Rationalists such as Descartes and Spinoza held that reason alone can reach important truths, independent of experience. Empiricists such as Locke and Hume held that knowledge comes from sensory experience; Locke compared the newborn mind to a blank slate. Kant tried to settle the debate by arguing that experience supplies the content of knowledge while the mind supplies its structure.

Are the portraits of ancient philosophers real likenesses?

No one knows exactly what Socrates, Plato, Confucius or the Buddha looked like. The Greek busts on this page are Roman marble copies of lost Greek originals, the Confucius image is a Han-dynasty tomb fresco painted centuries after his death, and the Buddha is a Sarnath sculpture made many centuries after his lifetime. They show how later artists imagined these thinkers.

Which philosophers explained why people do what they do?

Almost all of them, in different words. Socrates blamed ignorance, Aristotle pointed to habit and virtue, the Buddha to desire and attachment, Hume to passion over reason, Marx to economic conditions, Freud to unconscious drives and Sartre to the weight of freedom. This page groups 25 thinkers into six answers: reason, emotion, habit, inner drives, society and freedom.