Beauty is the quality of a thing that makes it pleasurable to see. It can be found in landscapes, sunsets, humans or works of art. It is a subjective pleasure that is often contrasted with ugliness as its negative counterpart.

There are two main conceptions of beauty: one in which it consists of a symmetrical relationship of parts, such as the golden ratio; and another that is more subjective, based on a sense of harmony between parts. Both of these ideas are attested in the early Western tradition, and were reflected in classical architecture, sculpture, literature, music and the mathematical sciences throughout the ancient world.

Originally, beauty was the objective quality of an object, in that it possessed definite proportions and relations among parts that could be measured and reproduced reliably. For example, Euclid’s ‘golden section’ (Euclidean geometry) was regarded as a symbol for beauty. The symmetrical relationships of the parts were thought to be essential to a beautiful object; it was also possible to reproduce the exact proportions and relations of the ‘golden section’ in other objects.

The earliest Western philosophers, especially Plato and Aristotle, believed that beauty could be understood by studying its symmetry, proportion and harmonious relations between parts. These concepts were derived from an ancient belief that all parts of the universe had the same nature, and that they could be arranged in such a way that they produced a coherent whole.

Thomas Aquinas adapted these principles to Christianity, and connected the concept of beauty to the Second Person of the Trinity, who was said to be “beautiful” when his attributes were complete by their own interior logic. He gave three qualifications for something to be considered beautiful: it must have integrity, it must have due proportion or consonance, and it must be clear in its appearance.

Aquinas’s concept of beauty was later refined by philosophers such as Edmund Burke, who interpreted beauty as a series of qualities that only have meaning insofar as they act on the mind through the senses. Burke argued that these qualities were “not in themselves good or bad,” but merely “good and bad” insofar as they made sense to human minds.

In the 18th century, with its emergence of confidence in human capability, emergent sense of inalienable rights and burgeoning cultures of feeling, aesthetic thinking began to shift from mathematical thinking and the divine to more subjective approaches. Aristotle’s notion of beauty was no longer the most important goal of philosophy, and even Hume and Kant largely abandoned it in favor of a more subjective account of taste, based on the individuality of each mind and its ability to perceive its own particular beauty.

In the twentieth century, though, a return to a more objective conception of beauty was often combined with a tendency to associate it with power, particularly political power. This association made beauty seem insubstantial and undeserving of serious reflection, so that, as Arthur Danto has shown, it became a subject of moral and political critique.