Anaxagoras: Biography, Philosophy & Quotes

Instructor: Erica Cummings

Erica teaches college Humanities, Literature, and Writing classes and has a Master's degree in Humanities.

Anaxagoras was a Pre-Socratic Greek philosopher with some unique ideas about where the world came from and how the world came into being. Let's explore the life and philosophy of Anaxagoras.

Introduction and Biography

Anaxagoras was an ancient Greek Pre-Socratic philosopher who developed theories on the substance and the formation of the universe. Anaxagoras was born circa 500 BCE into an aristocratic family in Clazomenae (modern day Turkey). He later moved to Athens, Greece, in order to further pursue philosophy. In fact, he may be the first person to study philosophy as its own discipline in Athens. His philosophy influenced several thinkers in Athens, including Pericles (the leader and politician), Euripides (the dramatist), and Aristophanes (the comic playwright).


Like other Pre-Socratic philosophers of his time, Anaxagoras chose to interpret the world through a lens of science, observation, and logic instead of through traditional Greek mythology. Because of this rejection of traditional Greek mythology, Anaxagoras was convicted of atheism and exiled from Athens in the 430s. While many rejected his ideas as dangerous, he helped start the trend of philosophical thought in Athens that would be carried on by major thinkers like Plato and Aristotle.

Anaxagoras wrote perhaps one book, but we have only fragments of his writings. Later philosophers like Plato and Aristotle also discussed the philosophy of Anaxagoras, so they shed some light on this figure as well. From what we do know of his philosophy, we can discern his ideas on three major topics, which we will explore below: (1) the substance of the universe, (2) the formation of the universe, and (3) explanation of natural phenomenon.

1. The Substance of the Universe

The Pre-Socratic philosophers observed that the world is made up of very diverse objects, and they all attempted to develop theories that explained this diversity. Anaxagoras theorized that there are numerous (perhaps infinite) fundamental, physical substances that combine in unique ways to construct this diversity we see. Anaxagoras never listed what these fundamental substances were, so we must assume that these substances refer to both opposing forces (hot-cold, light-dark, etc.) and elements (fire, water, bone, flesh, etc.). These fundamental substances act sort of like ingredients that combine in certain ratios to produce different things or beings on Earth. These things (like trees, furniture, etc.) and beings (humans, animals) thus have a sort of secondary existence because they are composed of fundamental substances.

Anaxagoras insisted on a few main principles when it comes to these fundamental substances:

(A) There is no becoming and no passing-away. In other words, these fundamental substances have always existed. Nothing can ever be truly created from nothing and likewise, nothing ever truly goes out of existence. For example, when people die, they do not truly cease to exist. Instead, the fundamental substances that composed them simply separate.

(B) Everything is in everything. This principle means that all of these fundamental substances are inextricably intertwined. Therefore, we can never find one of these fundamental substances in its purity; all of the other fundamental substances are always present. For example, a dog is made up of the exact same fundamental substances as both a human and a chair. It's just that the ratio of these fundamental substances differs in each object or being. This is an odd concept, so consider this analogy: smear together red, green, blue, and yellow paint. Once you smear these colors together, you can never truly separate them again. The colors literally seem to be in one another.

(C) The principle of predominance states that a thing's appearance is determined by whatever fundamental substance(s) dominate that thing's makeup. To go back to our smeared paint example, if you add more green paint, what you see may look totally green to you because the green predominates over the other colors. But remember that remnants of the other colors will always be there, even if they are infinitesimally small, because, after all, nothing can go out of existence.

Painting of Anaxagoras
Painting of Anaxagoras

2. The Formation of the Universe

Now that we know what composes the universe, we may ask, who controls the universe? Who or what determines the way that different fundamental substances combine to form objects? Anaxagoras calls the force that orders the universe nous, which is the Greek word for 'reason' or 'mind.' Nous is responsible for the creation and the structure of the universe; it is the one thing that is external to and separate from the fundamental substances. Nous is similar to the Judeo-Christian God or to some Greek gods and goddesses, but Anaxagoras never links nous to a specific deity (and remember that Anaxagoras was actually considered an atheist). Instead, nous is an impersonal, perhaps amoral force.

Anaxagoras says that the universe began as a sort of blob of all these fundamental substances. At some point, nous literally began rotating this massive blob of fundamental substances. This rotation caused the fundamental substances to interact in certain ways, thus creating all physical things. Nous is thus the cause of all motion, and nous also currently maintains this rotation. Similar to the human mind, nous is the rational force that organized (and still organizes) the whole world.

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