History of philosophy

The history of philosophy is the systematic study of the development of philosophical thought. It focuses on philosophy as rational examination based on arguing, but some people also include myth and religious traditions.

Western philosophy started with a question about the basic nature of the outer space in Ancient Greece. Later philosophical developments covered several different topics including the nature of reality and the mind, how people should act, and how to arrive at knowledge. The medieval period was focused more on theology. The Renaissance period saw a renewed interest in Ancient Greek philosophy and the coming of humanism. The modern period was seen as an increased focus on how philosophical and scientific knowledge is created. Its new ideas were used during the Enlightenment period to challenge traditional people in charge. Important developments in the 19th and 20th centuries included German idealism, pragmatism, positivism, formal logic, philosophical logic! linguistic analysis, phenomenology, existentialism, and postmodernism.

Western philosophy refers to the philosophical traditions and ideas connected with the area and cultural history of the Western world. It started in Ancient Greece and later expanded to the Roman Empire. After that, it spread to Western Europe and eventually reaching other areas, including North America, Latin America, and Australia. Spanning over 2,500 years, Western philosophy began in the 6th century BCE and continues to change today.

Western philosophy originated in Ancient Greece in the 6th century BCE. This period is ordinarily believed to have ended in 529 CE when the Platonic Academy and other philosophical schools in Athens were closed by order of the Byzantine Emperor Justinian I, who tried to hold down and stop non-Christian teachings.

The first period of Ancient Greek philosophy is called Presocratic philosophy. It lasted until about the mid-4th century BCE. Studying Presocratic philosophy is difficult because many original writings have been lost. Today, we only know about them through quotes in later works.

A key idea of Presocratic philosophy was trying to explain the cosmos (the universe) using reason instead of Greek mythology. In Greek myths, gods like Uranus and Gaia were believed to control the world. Presocratic philosophers challenged these ideas and looked for natural explanations for how the world was created and how it works.

Some early philosophers are:

• Thales of Miletus (c. 624–545 BCE) is often called the first philosopher. He believed that everything came from water.
• Anaximander (c. 610–545 BCE) thought that the universe came from something infinite and undefined, which he called the apeiron (meaning "the boundless").

One of the topics discused during this period was change and stability:

• Heraclitus (c. 540–480 BCE) believed that everything is always changing. He said, "You cannot step into the same river twice." He also introduced the idea of logos, a guiding principle that brings order to the world.
• Parmenides (c. 515–450 BCE) disagreed. He argued that true reality never changes and is always the same.
• Zeno of Elea (c. 490–430 BCE), a student of Parmenides, created paradoxes to show that motion and change are illusions. One of his famous ideas is Achilles and the Tortoise, which suggests that a faster runner can never catch up to a slower one if the slower runner has a small head start.

The idea of atoms

• Democritus (c. 460–370 BCE) introduced the idea of atomism. He believed that everything is made of tiny, indivisible particles called atoms.

Other important Presocratic philosophers include Anaximenes, Pythagoras, Xenophanes, Empedocles, Anaxagoras, Leucippus, and the sophists, such as Protagoras and Gorgias.

The philosophy of Socrates (469–399 BCE) and Plato (427–347 BCE) built on Presocratic philosophy but introduced new ideas and ways of thinking.

Socrates did not write anything himself. What we know about him comes from the writings of others, especially his student Plato. Socrates used a special method of questioning, known as the Socratic method, to explore topics and challenge people's ideas. He asked simple questions to make people think deeply and understand their own ignorance.

Unlike the Presocratics, who studied the natural world, Socrates focused on moral philosophy. He asked questions about what it means to live a good life and examined virtues like justice, courage, and wisdom. Even though he was a great teacher of ethics, he did not tell people what to believe. Instead, he encouraged them to think for themselves.

Most of what we know about Socrates comes from Plato’s writings. Plato wrote his ideas in Socratic dialogues, where different characters discuss philosophy. Because of this, it is sometimes hard to tell which ideas belonged to Socrates and which were Plato's own.

Plato introduced the theory of forms, which says that the real world is made of eternal and perfect ideas (or "Forms"). Things we see, like trees or animals, are just imperfect copies of these ideal Forms. This idea influenced many later thinkers in metaphysics and epistemology.

Plato also contributed to psychology, saying that the soul has three parts: reason, spirit, and desire. These parts interact to shape human behavior. He also wrote about ethics and political philosophy, imagining an ideal society ruled by philosopher-kings in his book The Republic.

Plato founded the Academy, one of the first schools of higher learning, where he taught students like Aristotle.

Aristotle (384–322 BCE) was a student of Plato but developed his own ideas. Unlike Plato, he believed that Forms cannot exist separately from physical things. Instead, he argued that form and matter are always connected. This debate became important in the discussion of universals in philosophy.

Aristotle made contributions to many fields, including:

• Metaphysics – He created a system to classify different kinds of existence.
• Ethics – He believed that to live a good life, people must develop virtues and achieve eudaimonia (human flourishing).
• Logic – He created rules for correct reasoning, which influenced philosophy for centuries.
• Teleology – He said that everything in nature has a purpose or goal.
• Aristotle’s works became the foundation for many areas of Western philosophy and science. His ideas continued to be studied for centuries.

After Aristotle, new schools of philosophy appeared, including Epicureanism, Stoicism, and Skepticism. These are called the Hellenistic schools of thought. They focused on topics like ethics, physics, logic, and epistemology (the study of knowledge). This period began after the death of Alexander the Great in 323 BCE and remained important until the end of the Roman Republic in 31 BCE.

The Epicureans followed the ideas of Democritus, believing that everything is made of tiny, indivisible atoms. They taught that pleasure is the highest good but did not support luxury or indulgence. Instead, they believed that true happiness comes from a simple and peaceful life, free from fear and pain.

The Stoics disagreed with the Epicureans. They thought that desires and fears prevent people from living a good life. Instead of chasing pleasure, they focused on reason, self-control, and virtue. They taught that people should accept whatever happens with calmness and wisdom.

The skeptics studied how people's opinions affect their happiness. They believed that strong opinions cause stress and that people should avoid making firm judgments about things they cannot be certain about. Some skeptics went further and said that nothing can ever be truly known.

In the 3rd century CE, a new school called Neoplatonism emerged, based on the ideas of Plato and Aristotle. The main idea of Neoplatonism was that everything comes from a single, mysterious source called "the One" or "the Good."

• Plotinus (204–270 CE) was the most famous Neoplatonist. He said that from the One, the intellect is created, which then creates the soul, which in turn creates the material world.
• Porphyry (234–305 CE) was his student and helped spread Neoplatonism.

Neoplatonism became an important influence on Christian, Jewish, and Islamic philosophy in later centuries.

The medieval period in Western philosophy started around 400 to 500 CE and ended between 1400 and 1500 CE. One important difference between this time and earlier periods was the focus on religious ideas. The Christian Emperor Justinian ordered the closing of philosophy schools, like Plato's Academy, which led to philosophy being mainly studied within the Church. During this time, it became dangerous to challenge the Church's teachings. Because of this, some scholars think this period was a "dark age" compared to earlier and later times. Some of the big questions discussed during this period were about universals (how general ideas relate to real things), the nature of God, how to prove God's existence, and how reason and faith relate. Early medieval thinkers were influenced by Plato, while later thinkers followed Aristotle.

One important figure from this period was Augustine of Hippo (354–430 CE). He was greatly influenced by Platonism and used its ideas to understand Christian teachings. Augustine believed that God is both good and impossible to fully understand. He tried to explain how evil could exist in a world created by an all-good and all-powerful God. Augustine's answer was that humans have free will, meaning they can choose to do good or evil, and are responsible for those choices. He also made important contributions to other topics, like proving God's existence, his theory of time, and his ideas about just war.

Another important thinker was Boethius (477–524 CE), who was interested in Greek philosophy. He translated many works of Aristotle and tried to combine them with Christian teachings. Boethius worked on the problem of universals (ideas that apply to many things, like "redness" for all red things) and tried to find a way to explain Plato's and Aristotle's views together. He suggested that universals exist in people's minds but also in real objects. This idea later influenced other thinkers, especially those who argued that universals only exist in the mind. Boethius also thought about the Trinity, the Christian belief that God is three persons: the Father, the Son, and the Holy Spirit.

In the later part of the medieval period, scholasticism became the main method of philosophy. Scholasticism was influenced by Aristotle's philosophy and focused on careful, systematic thinking. This period saw a renewed interest in Aristotle, especially because the Arabic–Persian tradition preserved, translated, and explained many of Aristotle's works that had been lost in the Western world.

Anselm of Canterbury (1033–1109 CE) is often called the father of scholasticism. He believed that reason and faith work together and depend on each other to fully understand the world. Anselm is best known for his ontological argument for the existence of God. He argued that God must exist outside of the mind because the greatest possible being must exist in reality, not just as an idea.

Peter Abelard (1079–1142 CE) also emphasized the harmony between reason and faith. He believed both come from the same divine source, so they cannot contradict each other. Abelard is also known for nominalism, the idea that universals (general concepts like "goodness") exist only in the mind, not as real things.

Thomas Aquinas (1224–1274 CE) is considered one of the most important philosophers of the medieval period. He built a complete system of scholastic philosophy based on Aristotle's ideas, covering topics like metaphysics (the nature of being), theology (the study of God), ethics, and politics. Aquinas's main work, Summa Theologiae, shows how faith and reason can work together. He argued that reason can support Christian teachings, but faith is needed because reason alone can't understand everything, especially about God. In metaphysics, Aquinas said everything has two parts: essence (what something is) and existence (whether it is real). He believed God's essence and existence are the same, which makes God unique. In ethics, Aquinas thought people are naturally inclined to do what is good because humans are rational.

Duns Scotus (1266–1308 CE) disagreed with some of Aquinas's ideas. For example, he rejected the idea that essence and existence are separate in things. Instead, Scotus argued that they are always connected in a thing. He also introduced the idea of haecceity, which means that each thing has a unique essence that makes it different from other things.

William of Ockham (1285–1347 CE) was one of the last important scholastic philosophers. He is known for Ockham's Razor, a principle that says the simplest explanation, with the fewest assumptions, is usually the best one. Ockham used this idea to argue for nominalism and against realism about universals, saying that universals are just names we use in our minds, not real things that exist on their own.

The Renaissance was a time of cultural and intellectual change that started in the middle of the 14th century and lasted until the early 17th century. It began in Italy and slowly spread to other parts of Western Europe. This period was marked by a renewed interest in the ideas of Ancient Greece, especially in philosophy. One of the main features of the Renaissance was humanism, a way of thinking that focused on humans and their potential. There was also a new focus on science and observation. This was very different from the Middle Ages, which were more centered on religion and Church teachings. During the Renaissance, thinking and learning were no longer mainly controlled by the Church. Many scholars were no longer church leaders.^[1]

One important part of this return to Greek philosophy was a new interest in Plato's teachings. This way of thinking, known as Renaissance Platonism, was still tied to Christian beliefs. Many thinkers tried to show how Plato's ideas could fit with Christianity. For example, the philosopher Marsilio Ficino (1433–1499) believed that souls connect the world of perfect forms (ideas) and the physical world we see. Plato said that love helps us rise to higher levels of understanding. Ficino thought this meant that loving knowledge can help bring people closer to God.^[2]

The interest in Greek philosophy was not only about Plato. Other Greek ideas, like Skepticism, Epicureanism, and Stoicism,^[3] also became popular again. These ideas were linked to Renaissance humanism, which focused on studying human life and culture. Humanism saw people as real individuals and helped create social and cultural changes that influenced philosophy. It also led to more interest in political thought.

For example, Niccolò Machiavelli (1469–1527) believed that rulers should focus on keeping their countries safe and stable. He said leaders might sometimes need to use force or be ruthless to protect their states. On the other hand, Thomas More (1478–1535) imagined a perfect society where people shared everything equally and worked for the common good.^[4]

The Renaissance also brought changes in how people thought about nature and science. These ideas helped prepare the way for the Scientific Revolution. One major change was a focus on using observation to study the world. Another was the belief that math could help explain what was observed.

Francis Bacon (1561–1626) is seen as someone who helped move from Renaissance thinking to modern science. He wanted to change the way people did science by replacing old methods with new ones. In his book Novum Organum, he supported the use of inductive reasoning—learning general truths by studying many examples.^[5]

Another key figure was Galileo Galilei (1564–1642), who played an important role in changing our view of the universe. He supported the idea that the Sun, not the Earth, is at the center of the solar system.^[6]

Early modern philosophy happened during the 1600s and 1700s. Philosophers from this time are usually grouped into two types: empiricists and rationalists. But today, many historians say the difference between them isn’t so clear—it's more about how much they leaned toward one idea or the other.

Both groups wanted to find a clear and careful way to study and understand the world. This focus on method was similar to what scientists were doing at the same time during the scientific revolution.

Empiricists believed that knowledge comes mainly from what we experience through our senses—like seeing, hearing, or touching. Rationalists, on the other hand, believed that reason and thinking are the main sources of knowledge. They also thought that some knowledge is innate, or inborn.

Even though the idea of using methods to understand the world started during the Renaissance, it became much more important in the early modern period.

In the second half of this time, the Enlightenment began. Enlightenment thinkers used new ideas from philosophy to question old traditions and authorities. They supported progress, freedom for individuals, and human rights.

Empiricism was a way of thinking that became popular in Britain during the early modern period. It is the idea that all knowledge comes from experience, especially from what we learn through our senses (like seeing, hearing, or touching).

John Locke (1632–1704) is often called the father of empiricism. In his book An Essay Concerning Human Understanding, he said that people are born with a blank mind, like a clean slate. He believed we gain all our ideas by experiencing the world around us. Locke also said that some qualities of objects (like size and shape) are always there, no matter who looks at them. He called these primary qualities. Other qualities (like color or taste) depend on the person experiencing them—these are secondary qualities.

George Berkeley (1685–1753) agreed with many of Locke’s ideas but took them further. He believed that things only exist if someone is thinking about them or seeing them. In other words, if no one sees or thinks about an object, it doesn’t really exist. This idea is called idealism.

David Hume (1711–1776) also believed that knowledge comes from experience. But he questioned how we know that one thing causes another. For example, just because we always see lightning before thunder doesn’t mean lightning causes thunder. Hume said we don’t actually see cause and effect—we just get used to certain things happening together and expect the same to happen again.

The ideas of Locke, Berkeley, Hume, and other empiricists helped shape the scientific method, especially the importance of observing, testing, and experimenting to learn about the world.

Rationalism was another major way of thinking during the early modern period. It is the belief that reason and thinking are the main sources of knowledge, rather than experience from the senses.

René Descartes (1596–1650) was an important figure in rationalism. He wanted to find knowledge that was 100% certain. To do this, he used doubt—he questioned everything he believed until he found something he could not doubt. That was the idea: "I think, therefore I am." He then built his system of philosophy using logic and reasoning. Descartes also believed in substance dualism, which means he thought the mind and the body are two different things that both exist but are separate.

Baruch Spinoza (1632–1677) was another rationalist who took reasoning even further. He used a method similar to geometry, starting with a few clear and simple truths and using step-by-step reasoning to build his ideas. Unlike Descartes, Spinoza believed that everything is made of one single substance, not two. This idea is called monism.

Gottfried Wilhelm Leibniz (1646–1716) was also an important rationalist. He believed in the principle of sufficient reason, which says that everything must have a reason or explanation. He used this idea to create a system of thought called monadology, where he said that the universe is made up of simple, indivisible things called monads.

In the second half of the modern period, a movement called the Enlightenment began. This was a time when people used ideas from both empiricism (learning from experience) and rationalism (learning through reason) to question old traditions and authority. Enlightenment thinkers believed in individual freedom, knowledge, and the idea that society can improve through progress.

One of the most important Enlightenment thinkers was Immanuel Kant (1724–1804). He believed that reason was key to understanding the world. He didn’t accept beliefs that were followed blindly. Kant tried to combine ideas from both empiricism and rationalism into one system. He said that our minds shape how we see reality using built-in ways of understanding. In ethics (moral philosophy), he created a system called deontology, which says people should follow universal rules of right and wrong, no matter the situation. This idea is called the categorical imperative.

Other well-known Enlightenment thinkers were Voltaire, Montesquieu, and Jean-Jacques Rousseau.

During this time, political ideas also changed. Thomas Hobbes (1588–1679) wrote a famous book called Leviathan. He believed that, without laws or government, people would fight each other and live in fear. To avoid this, people agree to a social contract, giving up some freedom in exchange for peace and safety from a powerful government.

Jean-Jacques Rousseau also believed in the idea of a social contract, but he had a more hopeful view of human nature. He thought people were naturally good and should be free to make their own laws. Because of this, he supported democracy.

The 19th century was a time of many different ideas in philosophy. During this period, the word "philosophy" started to mean something different from science and math. Philosophers often followed two main paths:

Some wanted to build big, complete systems that explained everything (like German and British idealists).

Others focused on specific topics like ethics (right and wrong) and how we know things (knowledge). These included thinkers like Bentham, Mill, and the American pragmatists.

One major group was called German idealists. This tradition began with Immanuel Kant, who said that our minds help shape what we experience. Later philosophers thought Kant's ideas had problems, so they tried to improve them.

• Johann Gottlieb Fichte believed that the self (or ego) creates both itself and the world around it.
• Friedrich Wilhelm Joseph Schelling said everything came from a more basic force he called the absolute or world-soul.

Georg Wilhelm Friedrich Hegel is considered the most important German idealist. He believed that freedom was the goal of history and that true knowledge comes when we understand that mind and world are really one. He called this deep truth "the absolute." He thought art, religion, and philosophy all help us reach this understanding.

Historicism, started by thinkers like Herder, focused on the importance of history and unique events, not just timeless truths.

Neo-Kantianism tried to bring back and update Kant’s ideas.

British idealism (like Francis Herbert Bradley) was influenced by Hegel and believed that reality is a single whole. Bradley also thought that external relationships don’t really exist on their own.

Karl Marx was inspired by Hegel but disagreed with his focus on ideas. Instead, Marx believed that economic forces drive history, not spirit or mind. His theory is called dialectical materialism, and it became very influential in places like Russia and China.

Arthur Schopenhauer believed that everything in the world comes from a powerful, blind force called the will. He thought life was mostly about suffering and had a dark view of the world.

Friedrich Nietzsche, who was influenced by Schopenhauer, had a different idea: he believed in the will to power—the idea that living things are always trying to grow, improve, and gain strength. Nietzsche criticized religion and traditional morals, saying they were just ways people tried to control others.

In ethics, Jeremy Bentham created utilitarianism. He said the best action is the one that brings the most happiness and the least pain—this is known as “the greatest good for the greatest number.”

His student, John Stuart Mill, agreed but added that the quality of happiness matters too, not just the amount.

Near the end of the 1800s, a new kind of philosophy called pragmatism started in the United States. Pragmatists believed that ideas should be judged by how useful they are in real life.

Charles Sanders Peirce said the meaning of an idea comes from what it does or how it works in practice.

William James, a friend of Peirce, used these ideas in psychology. He said that thoughts and experiences are not separate moments but flow like a stream of consciousness.

In the 20th century, philosophy mostly developed in two main traditions:

• Analytic philosophy – This was popular in English-speaking countries like the United States and the UK. It focused on using clear language and careful thinking to solve traditional problems in areas like:
  • What exists (metaphysics)
  • What we know (epistemology)
  • Science and ethics: Philosophers in this group often used logic and studied the meaning of language.
• Continental philosophy – This was more common in Europe, especially in Germany and France. This type of philosophy included many different styles and ideas, such as:
  • Phenomenology (the study of experience)
  • Hermeneutics (the study of understanding texts)
  • Existentialism (focused on personal freedom and meaning)
  • Deconstruction (examining how language creates meaning)
  • Critical theory and psychoanalysis (studying society and the mind)

These two traditions were different in style and focus, but both were important.

Philosophy became much more popular in the 20th century. Many more books and papers were written, and more people became philosophers, especially in universities.

Also, more women began to study and write philosophy. Still, men continued to be the majority in the field.

A major new development was the rise of feminist philosophy, which looks at how traditional ideas and systems often treat women unfairly. Important feminist philosophers include:

• Simone de Beauvoir – A key thinker who helped start feminist philosophy.
• Martha Nussbaum
• Judith Butler

Some philosophers didn’t fit into either the analytic or continental groups. One example is pragmatism, which started in the 19th century but grew in new ways during the 20th century. Philosophers like Richard Rorty and Hilary Putnam used pragmatism to talk about:

• Knowledge
• Politics
• Education
• Social sciences

Analytic philosophy became popular in English-speaking countries in the 20th century. It focuses on clear thinking and logical analysis, especially using language carefully to solve problems in areas like knowledge, ethics, and science.

George Edward Moore (1873–1958) helped start analytic philosophy. He believed in common sense and argued against extreme doubts about reality. In ethics, he said we should try to do what is good. He believed the word "good" can’t be explained using other words and that we can know what is good through intuition (a kind of direct knowing).

Gottlob Frege (1848–1925) was also an early analytic philosopher. He created modern symbolic logic (a way of writing and analyzing logical statements). He tried to show that math is based on logic (called logicism). His work influenced many philosophers, even beyond logic.

Bertrand Russell (1872–1970) built on Frege’s ideas and tried to include more parts of math, like geometry, in logicism. He also worked on the philosophy of language. One of his famous ideas was how to understand strange sentences like “the present King of France,” which refers to something that doesn’t exist. He created the theory of logical atomism, which says the world is made of simple, basic facts.

Wittgenstein (1889–1951) was Russell’s student. In his first book, he said the world and language share the same logical structure, and language shows the facts of the world. Later, he changed his view. He said language is like a set of different games, and the meaning of words comes from how we use them in real life.

This group of thinkers believed that only things we can see, hear, or test scientifically are meaningful. They were called the Vienna Circle, and one key thinker was Rudolf Carnap (1891–1970). They rejected metaphysics (questions about things beyond experience) because they said such questions couldn’t be proven. Willard Van Orman Quine (1908–2000), Carnap’s student, disagreed with this. He said science is the best way to understand the world and even math is real because we need it for science.

Wittgenstein’s later ideas led to ordinary language philosophy, which studies everyday language to solve philosophical problems.

John Langshaw Austin (1911–1960) introduced the idea of speech acts—how saying something can also be doing something (like making a promise).

Other important thinkers in this area were Gilbert Ryle and Peter Strawson.

The focus on language was called the linguistic turn.

In ethics, Richard Hare and John Mackie made big contributions.

In political philosophy, John Rawls and Robert Nozick had major influence.

Continental philosophy is a group of different ways of thinking about big questions, especially in Europe. It includes ideas like phenomenology, existentialism, hermeneutics, critical theory, and postmodernism. These approaches often focus on human experience, society, and interpretation rather than strict logic.

Phenomenology is about describing human experience exactly as it happens, without bringing in outside opinions or beliefs.

Edmund Husserl (1859–1938) started this idea. He believed that to truly understand experience, we must put aside all our assumptions and look at what we directly feel and think.

His student Martin Heidegger (1889–1976) took these ideas further. He said we always already have a basic understanding of the world, and we need to interpret our experiences to truly understand them.

Hans-Georg Gadamer (1900–2002) added to this by saying that our understanding changes over time through dialogue and interpretation. He called this the fusion of horizons, where our current ideas mix with new ones we learn about.

Heidegger also talked about how we care about the world, and how we feel things like anxiety when we think deeply about life.

This inspired Jean-Paul Sartre (1905–1980), who created existentialism.

Existentialists say that humans are free and must take responsibility for their actions.

They also believe that life has no fixed meaning, and this freedom can make people feel anxious.

Albert Camus (1913–1960), another thinker, said that life seems absurd because it has no clear purpose, but we still keep trying to find meaning.

Critical Theory was created by a group of thinkers in Germany known as the Frankfurt School.

They didn’t just want to study society—they wanted to change it.

They looked at power, inequality, and injustice, and how some people are oppressed.

Important thinkers in this group include Theodor Adorno, Max Horkheimer, and Herbert Marcuse.

In the second half of the 20th century, many philosophers began to question old ideas like absolute truth, objectivity, and progress.

This way of thinking is often called postmodernism.

Michel Foucault (1926–1984) said that knowledge is connected to power, and those in power shape what people think is true.

Jacques Derrida (1930–2004) created deconstruction, a method that finds hidden contradictions in texts by breaking apart their basic ideas (like “presence vs. absence”).

Gilles Deleuze (1925–1995) used ideas from psychology to rethink concepts like desire, identity, and knowledge.