Greek philosophy is one of the oldest and most influential branches of philosophical thought in Western culture. It began with the pre-Socratic philosophers, who sought to explain natural phenomena without relying on religious explanations. This was followed by the Sophists, who argued that knowledge could be obtained through observation and debate rather than divine revelation or tradition. The classical period saw the flourishing of philosophical schools such as Platonism, Epicureanism, Stoicism, Pyrrhonism, and Skepticism, which continued into the Hellenistic period alongside Aristotelianism and Neoplatonism. Later thinkers such as Plotinus developed these ideas further before they were eventually incorporated into Christianity during Late Antiquity.

The roots of Greek philosophy lie in ancient Ionian Greece, where thinkers such as Thales attempted to explain natural phenomena using rational arguments rather than mythology or religion. Thales believed that all things are composed of water, while other early pre-Socratics proposed various forms of material monisms, including air (Anaximenes) or fire (Heraclitus). These early attempts at scientific explanation led to more sophisticated theories from Plato onward, which emphasized mathematics and logical argumentation over physical evidence alone.

In addition to their focus on nature, many Pre-Socratic philosophers also laid out ethical systems based upon reason rather than faith or tradition; this type of moral reasoning would later become known as virtue ethics. Socrates famously claimed that "the unexamined life is not worth living," meaning that true happiness comes from understanding oneself and questioning accepted beliefs about morality instead of simply following what society dictates should be done. He founded his own school called the Academy, where he taught students how to think critically about traditional values like justice and beauty before being sentenced to death for corrupting youth's minds by challenging conventional wisdom too much.

Plato's student Aristotle expanded upon Socrates' teachings by developing an empirical approach towards understanding reality combined with formal logic techniques for arriving at valid conclusions from premises; this became known as syllogistic logic, which remained popular until modern times when it was replaced by mathematical logic due to its greater precision. His writings cover almost every field imaginable, ranging from physics, metaphysics, psychology, politics, and biology, all the way up to poetry. Many aspects still form part of our contemporary education system today, thanks largely to the influence gained via medieval Scholasticism.

From around 300 BCE onwards, new philosophical schools began appearing throughout Ancient Greece whose primary goal was to provide guidance on how to best live one's life so long-term fulfillment could be achieved despite the constant flux of change surrounding them; examples include Cynics (led by Diogenes), Epicureans (Epicurus), Stoics (Zeno), etc., each having distinct views regarding human behavior but shared belief that wisdom comes by engaging the world rationally as opposed to superstition and fear.