Art theory is the reasoned discussion or analysis of works of art. As a discipline, it includes all aspects of the production, reception, and criticism of art. It is distinguished from art history, which primarily concerns itself with the historical development of aesthetic movements, ideas, and trends.

One of the earliest theorists to write about art was Plato, who argued that art was a means of expression and communication that had the power to educate or illuminate its viewers. For Plato, art was an imitation of reality, and he believed that it had the ability to improve the human soul.

Aristotle also wrote about art, but his focus was on the function of art, rather than its form or aesthetics. Aristotle believed that art was a means of achieving a particular end, such as catharsis (the purging of emotions) or education.

The Italian Renaissance thinker Leon Battista Alberti also wrote about the role of art, and he is generally considered to be the first art theorist of the modern era. In his treatise On Painting, Alberti argued that the function of art was to represent reality in a way that was pleasing to the eye and accessible to the intellect.

The German philosopher Immanuel Kant also wrote about art, and he is often credited with establishing the discipline of aesthetic philosophy. Kant believed that art existed for its own sake and was not simply a means to an end. He also argued that the experience of art was subjective and that each viewer brought their own individual perspectives and interpretations to the work.

In the late 19th century, a group of thinkers known as the Russian Formalists began to challenge some of the traditional ideas about art. The Formalists argued that art should be judged on its own merits, rather than in relation to its historical or social context.

The French philosopher Jacques Derrida also wrote about art, and he is considered one of the most important post-structuralist thinkers. Derrida argued that all art is fundamentally unstable and that meaning is always deferred or postponed.

Art theory is a complex and ever-evolving field of inquiry, and there are many different schools of thought. However, all art theorists share a common interest in understanding the nature and function of art.