What makes art beautiful is a complicated concept, since beauty is subjective and can change based on context. However, there is a basic human instinct, or internal appreciation, for harmony, balance, and rhythm which can be defined as beauty. Beauty in terms of art usually refers to an interaction between line, color, texture, sound, shape, motion, and size that is pleasing to the senses.

Aesthetic Art

Aesthetics is the branch of philosophy that deals with the nature and appreciation of art, beauty, and taste. Aesthetics is central to any exploration of art. The word "aesthetic" is derived from the Greek "aisthetikos," meaning "esthetic, sensitive, or sentient. " In practice, aesthetic judgment refers to the sensory contemplation or appreciation of an object (not necessarily a work of art), while artistic judgment refers to the recognition, appreciation, or criticism of a work of art.

Numerous philosophers have attempted to tackle the concept of beauty and art. For Immanuel Kant, the aesthetic experience of beauty is a judgment of a subjective, but common, human truth. He argued that all people should agree that a rose is beautiful if it indeed is. There are many common conceptions of beauty; for example, Michelangelo's paintings in the Sistine Chapel are widely recognized as beautiful works of art. However, Kant believes beauty cannot be reduced to any basic set of characteristics or features. 

For Arthur Schopenhauer, aesthetic contemplation of beauty is the freest and most pure that intellect can be. He believes that only in terms of aesthetics do we contemplate perfection of form without any kind of worldly agenda.

Michelangelo, The Creation of Adam, The Sistine Chapel, 1508-1512

Beauty in art can be difficult to put into words due to a seeming lack of accurate language. An aesthetic judgment cannot be an empirical judgment but must instead be processed on a more intuitive level.

Art and Human Emotion

Sometimes beauty is not the artist's ultimate goal. Art is often intended to appeal to, and connect with, human emotion. Artists may express something so that their audience is stimulated in some way—creating feelings, religious faith, curiosity, interest, identification with a group, memories, thoughts, or creativity. For example, performance art often does not aim to please the audience but instead evokes feelings, reactions, conversations, or questions from the viewer. In these cases, aesthetics may be an irrelevant measure of "beautiful" art.