Understanding the nature and meaning of beauty is one of the key themes in the philosophical discipline known as aesthetics. The composer and critic Robert Schumann distinguished between two kinds of beauty, natural beauty and poetic beauty: the former being found in the contemplation of nature, the latter in man's conscious, creative intervention into nature. Schumann indicated that in music, or other art, both kinds of beauty appear, but the former is only sensual delight, while the latter begins where the former leaves off.

A common theory says that beauty is the appearance of things and people that are good. This has many supporting examples. Most people judge physically attractive human beings to be good, both physically and on deeper levels. The phrase "beauty is in the eye of the beholder," however, suggests that beauty is wholly subjective.

"Beauty as goodness" has many significant counterexamples with no agreed solution. These include such things as a glacier, or a ruggedly dry desert mountain range. Most people find beauty in nature, despite it sometimes being "red in tooth and claw" (Tennyson). Another type of counterexample are comic or sarcastic works of art, which can be good, but are rarely beautiful.

It is well known that people's skills develop and change their sense of beauty. Carpenters may view an out-of-true building as ugly, and many master carpenters can see out-of-true angles as small as half a degree. Many musicians can likewise hear as dissonant a tone that's high or low by as little as two percent of the distance to the next note. Most people have similar aesthetics about the work or hobbies they've mastered.

Beauty as a quantifiable and measurable attribute places upon the trained and educated viewer a great deal of responsibility to tolerate defect. Thus, beauty is in the eye of the beholder only so far as the beholder tolerates defect. It is indeed subjective but in relation to one's intelligence and understanding.

Cosmetology is the treatment of skin, hair and nails and includes, but is not limited to, manicures, pedicures, application of artificial nails, special occasion hairstyling, shampooing hair, cosmetic application, body hair removal, chemical hair relaxers or straighteners, permanent waves, coloring and highlighting of hair, and hair extensions or wig treatments. A person who is licensed in cosmetology is called a cosmetologist.

A cosmetologist sometimes called a beautician, a beauty specialist, or an esthetician or aesthetician, is a worker who specializes in giving beauty treatments. The recipients of these treatments are usually women. A general cosmetologist is proficient in all forms of beauty care and can give hair treatments, facials, skin treatments, and nail treatments.

There are specific disciplines of cosmetology that some cosmetologists may specialize in. The different types of special cosmetologists include hair stylists, shampooers, manicurists, estheticians and electrologists. Many cosmetologists specialize in at least one of these categories.

An esthetician, or aesthetician, specializes in the study of skin care, including facial treatments, waxing as a form of hair removal, and cosmetic make-up services. Some estheticians also offer full body skin treatments and other related services.

To become a cosmetologist in the United States, a state license is required. Each state mandates the amount of educational hours necessary before a practical exam may be taken. Some states also allow apprenticeships in hair salons under the guidance of a licensed cosmetology teacher, but this is quickly becoming obsolete. Safety guidelines and the threat of lawsuits have changed the salon environment, and kept apprentices away from the chair. These days it is beneficial for anyone interested in cosmetology to pursue the minimum qualifications of hairdressing. Cosmetology licenses must be renewed every two years. Licenses expire on December 31st of the expiration year. The State Board of Cosmetology [1] regulates how many, if any, continuing education units or hours are needed to maintain an active license in a particular state.

A difference also exists between beauty therapy and cosmetology. Beauty therapy involves itself with beautician or aestheticienne work (treatment of skin and nails, including manicures, pedicures, facials, waxing, facial electrical treatments, eyelash tinting, eyebrow tinting and other such treatments), physiatrics or body therapy work (Swedish massage, anatomy and physiology, body electrical treatments, body wraps, body treatments, figure analysis and cellulite treatments), and electrologywork or electrolysis. A cosmetologist instead deals with surface-only treatments. Beauty therapists can be qualified internationally through international bodies like ITEC, CIBTAC and CIDESCO.