Aesthetics is the study of art and beauty; it was an important issue for such 18th- and 19th-century philosophers as Kant or Hegel. Classical philosophers like Plato and Aristotle also theorized about art and painting in particular;

Plato disregarded painters (as well as sculptors) in his philosophical system; he maintained that painting cannot depict the truth—it is a copy of reality (a shadow of the world of ideas) and is nothing but a craft, similar to shoemaking or iron casting. By the time of Leonardo painting had become a closer representation of the truth than painting was in Ancient Greece. Leonardo da Vinci, on the contrary, said that "La Pittura è cosa mentale" (painting is a thing of the mind). Kant distinguished between Beauty and the Sublime, in terms that clearly gave priority to the former. Although he did not refer particularly to painting, this concept was taken up by painters such as Turner and Caspar David Friedrich.

Hegel recognized the failure of attaining a universal concept of beauty and in his aesthetic essay wrote that Painting is one of the three "romantic" arts, along with Poetry and Music for its symbolic, highly intellectual purpose. Painters who have written theoretical works on painting include Kandinsky and Paul Klee. Kandinsky in his essay maintains that painting has a spiritual value, and he attaches primary colors to essential feelings or concepts, something that Goethe and other writers had already tried to do.

Iconography is the study of the content of paintings, rather than their style. Erwin Panofsky and other art historians first seek to understand the things depicted, then their meaning for the viewer at the time, and then analyze their wider cultural, religious, and social meaning.

In 1890, the Parisian painter Maurice Denis famously asserted: "Remember that a painting—before being a warhorse, a naked woman or some story or other—is essentially a flat surface covered with colors assembled in a certain order." Thus, many 20th-century developments in painting, such as Cubism, were reflections on the means of painting rather than on the external world, nature, which had previously been its core subject. Recent contributions to thinking about painting have been offered by the painter and writer Julian Bell. In his book What is Painting?, Bell discusses the development, through history, of the notion that paintings can express feelings and ideas. In Mirror of The World Bell writes:

A work of art seeks to hold your attention and keep it fixed: a history of art urges it onwards, bulldozing a highway through the homes of the imagination.

Source: Wikipedia