Aesthetics
Aesthetics is a branch of philosophy dealing with the nature of beauty.
The word aesthetic can be used as a noun meaning "that which appeals to the senses."
Someone's aesthetic has a lot to do with their artistic judgment. For example, an individual who wears vintage clothing, drives a vintage car, and wallpapers their home with flowers has a particular aesthetic.
If something is anaesthetic, it tends to dull the senses or cause sleepiness.
In contrast, aesthetic may be thought of as anything that tends to enliven or invigorate or wake one up...whether the form be beautiful or not.
Aesthetics in art
Of course art appreciation is in the eyes of the beholder, although there are certain elements that we can define across a group of paintings that can be generalized or delineated, and hence discussed and analyzed on their own merits.
Generally, art adheres to the aesthetic principles of symmetry/asymmetry, focal point, pattern, contrast, perspective, 3D dimensionality, movement, rhythm, unity/Gestalt, and proportion.
Unfortunately you can't take a sample of artwork, lay it down, critique it across these dimensions, and reach some kind of quantitative judgment as to its quality.
Great paintings move us; but they may violate some guidelines or lend different weights to various principles.
What is Art .... ?
Art has not always been what we think it is today. An object regarded as Art today may not have been perceived as such when it was first made, nor was the person who made it necessarily regarded as an artist. Both the notion of "art" and the idea of the "artist" are relatively modern terms.
Many of the objects we identify as art today -- Greek painted pottery, medieval manuscript illuminations, and so on -- were made in times and places when people had no concept of "art" as we understand the term. These objects may have been appreciated in various ways and often admired, but not as "art" in the current sense.
Book of Kells, "The Four Evangelists."
An illuminated manuscript of the Gospels from mid-8th century Ireland.
Art lacks a satisfactory definition. It is easier to describe it as the way something is done -- "the use of skill and imagination in the creation of aesthetic objects, environments, or experiences that can be shared with others" -- rather than what it is.
During the 12th and 13th centuries, university curriculum consisted of seven Liberal Arts and did not involve creating anything at which people looked. They were:
To further confuse matters, these seven Arts were known as the Fine Arts, in order to distinguish them from the "Useful Arts". Why? Only "fine" people - those who didn't do manual labor - studied them. (Presumably, the Useful Arts people were too busy being useful to have need of an education.)
Albrecht Durer The Schoolmaster, 1510
Painting and sculpture were included among a number of human activities, such as shoemaking and weaving, which today we would call crafts.
Ed Paschke, Shoe Sack, 1973
Ed Paschke, Metal de bleu
The idea of an object being a "work of art" emerges, together with the concept of the Artist, in the 15th and 16th centuries in Italy.
Leonardo da Vinci, La Joconde (1479-1528)
During the Renaissance, the word Art emerges as a collective term encompassing Painting, Sculpture, and Architecture, a grouping given currency by the Italian artist and biographer Giorgio Vasari in the 16th century.
Subsequently, this grouping was expanded to include Music and Poetry which became known in the 18th century as the 'Fine Arts'. These five Arts have formed an irreducible nucleus from which have been generally excluded the 'decorative arts' and 'crafts', such as as pottery, weaving, metalworking, and furniture making, all of which have utility as an end.
The painter and the sculptor were now seen to be subject to inspiration and their activities equated with those of the poet and the musician.
In the latter half of the 16th century the first academies of art were founded, first in Italy, then in France, and later elsewhere.
The Accademia dell' Arte del Disegno (Academy of Design) of Florence was the first academy of Art in Europe. It was founded in 1561 with high patronage by Vasari.
The Accademia has housed the original David of Michelangelo since 1873, when it was moved there to protect it.
Pietro Francesco Alberti The Painters’ Academy,
c.1615. Etching
Academies took on the task of educating the artist through a course of instruction that included such subjects as geometry and anatomy. Out of the academies emerged the term "Fine Arts" which held to a very narrow definition of what constituted art.
The Fine (Visual) Arts
painting
sculpture
architecture
And the decorative arts
ceramics
furniture and interior design
jewelry making
metal crafting
wood working

Drawing from Life at the Royal Academy, by Rowlandson, Pugin and Bluck, 1808
The institutionalizing of art in the academies eventually provoked a reaction to its strictures and definitions in the 19th century at which time new claims were made about the nature of painting and sculpture.
By the middle of the 19th century, "modernist" approaches were introduced which adopted new subject matter and new painterly values.
In large measure, the modern artists rejected, or contradicted, the standards and principles of the academies and the Renaissance tradition.
By the end of the 19th century and the beginning of the 20th, artists began to formulate the notion of truth to one's materials, recognizing that paint is pigment and the canvas a two-dimensional surface.
At this time the call
also went up for "Art for Art's Sake."
A term applied to various exaggerations of
the doctrine that art is self-sufficient and need serve no ulterior purpose,
whether moral, political, or religious.
In the early 20th century all traditional notions of the identity of the artist and of art were thrown into disarray by Marcel Duchamp and his Dada associates. In ironic mockery of the Renaissance tradition which had placed the art institutions in an exalted authoritative position, Duchamp, as an artist, declared that it is false that only works of art have aesthetic value.
For the duration of the 20th century, this position has complicated and undermined how art is perceived but at the same time it has fostered a broader, more inclusive assessment of art.
Marcel
Duchamp Fountain (1917/1964)
A "Readymade" is an everyday object selected and designated as art.
Duchamp acquired the lavatory urinal for the original Fountain directly from J. L. Mott Iron Works, a manufacturer of plumbing equipment. Before submitting the piece to the exhibition as sculpture, the artist rotated the urinal ninety degrees from its normal, functional position, and left the piece unembellished except for the inscription "R. Mutt 1917" (a pseudonym that synthesized the name of the manufacturer and that of the popular comic strip "Mutt and Jeff").
The concept of the readymade lies not in the work itself, but in the idea behind
it. Emphasis is placed upon the artist "not as craftsman, but as gifted
perceiver whose choice of an object is seen as a creative act. The readymade
thus becomes the "focus of a meditation on the relation between external
things and our perception of them. Duchamp was using Fountain to show that
it is false that only works of art have aesthetic value.
"Whether Mr. Mutt with his own hands made the fountain or not has no importance. He CHOSE it. He took an ordinary article of life, placed it so that its useful significance disappeared under the new title and point of view - created a new thought for that object."
Summary of Aesthetic Principles
Keith Allen
The aesthetic experience consists in enjoying a thing for its own intrinsic beauty.
The nature of this enjoyment is differentiated by whichever emotions are predominant when that thing is being experienced. These emotions are without the objects they have in ordinary life.
When the emotion of love is evoked by a play, the viewer of the play does not fall in love with some character on the stage and attempt to carry away the actor portraying that character. When experiencing fear in the same context, the viewer does not believe himself actually to be in danger and flee the theater. In both cases, the emotion is experienced as divorced from the practical considerations with which the emotions of ordinary life are concerned.
The emotion evoked by a work of art is focused on the events and characters portrayed in that work, but it does not take them as its objects as would the ordinary emotions. Instead, the work of art evokes emotions that are relished as such, for their own sake.
When enjoying the intrinsic beauty of a work of art as tinged by the emotions evoked by it, even fear and revulsion can be sources of pleasure, as the work's beauty consists, in such cases, of its capacity to evoke these emotions.
As a work of art is what has the capacity to produce appreciation for its innate beauty, it serves no purpose beyond itself.
Didactic (morally instructive) content can be effectively included in an artistic work when it contributes to the production of a given emotion in the viewer, but when the purpose of a work is to convey information that work ceases to be art.
The purpose of a didactic work is to convey information, and once information has been learned it need not be learned again unless it is forgotten.
Having memorized my multiplication tables I have no need to memorize them again. If I review them, it is either because I do not know them, whether because of forgetfulness or my not having learned them when I was first presented them, or because I enjoy reviewing them, in which case I am not reviewing them in order to learn them but to relish some pleasure.
In contrast to this, I can read and reread a poem without learning anything from it, because the experience of relishing it for its own beauty does not entail acquiring any new knowledge.
The aesthetic experience is nothing other than the appreciation of a thing's beauty as colored by the particular emotions that thing evokes in the person having the experience. Art serves no other purpose and is clearly differentiated from practical activities such as learning.
Referring to nothing but itself, art is pragmatically useless, but existing only for itself and being deeply satisfying, it is in need of nothing else

Three of the most widely accepted criteria for determining whether or not something is a work of art are
(1) that the object or event is made by an artist,
(2) that the object or event is intended to be a work of art by its maker, and
(3) that important or “recognized” experts agree that it is a work of art.
Applied Art vs. Fine Art
The best applied art is and must be beautiful if it is to be effective at selling the product (or idea in the case of propaganda). Creating something visual for a practical end is what makes it applied.
Creating work for pay doesn't necessarily make it applied, it's just compensation to the artist for his work. It's when a work is created for another end, rather than just to be a work in itself, it becomes applied.
Photography vs. Painting