The Analysis of Beauty is a book written by William Hogarth (18th century English painter, satirist, and writer) and published in 1753, which describes Hogarth's theories of visual beauty and grace in a manner accessible to the common man of his day.
Prominent among Hogarth's ideas of beauty was the theory of the Line of Beauty; an S-shaped curved line (serpentine line) that excited the attention of the viewer and evoked liveliness and movement. The Analysis of Beauty formed the intellectual centrepiece of what the historian Ernst Gombrich described as Hogarth's "grim campaign against fashionable taste", which Hogarth himself described as his "War with the Connoisseurs".
In The Analysis of Beauty Hogarth implements six principles, which independently affect beauty. Although he concurs that those principles have an effect, he is not determinate on their specific influence. The first principle of beauty Hogarth describes is fitness, which is not in itself a source of beauty, but can be described as a material cause of it. Though the account of fitness on the total beauty of an object is only moderate, it is a necessary cause. Fitness does not necessarily imply purpose. However, improperly implied forms cannot be the source of beauty. It is in this that the necessity of fitness must be seen: if not accounted for, a form cannot readily be assumed beautiful.
The second major principle of beauty is variety. It is the source of beauty, which Hogarth shows us by the contrary notion of "sameness": "sameness", a lack of variety, offends the senses. "The ear is as much offended with one even continued note, as the eye is with being fix'd to a point, or to the view of a dead wall." In contrast, our senses find relief in discovering a certain amount of "sameness" within a varietal experience.
The third notion of regularity is understood as a form of "composed variety": it only pleases us when it is suggestive to fitness. Similar to this notion in effect is simplicity, which enhances the pleasure of variety in that it pleases the eye. The variety which causes a beautiful experience should, so to speak, be tempered by simplicity. On the other hand: simplicity without variety at best does only not displease.
Intricacy is a strange principle in that it does not directly follow from the formal behaviour of a beautiful object. Hogarth means by this the habit which causes us end up in the whirling game of pursuit, when bit by bit discovering the beauty of an object. Intricacy arises from the love of this pursuit. Every difficulty in understanding or grasping the object enhances the pleasure of overcoming it, to continue the pursuit. There is a direct connection here to the Line of Beauty Hogarth dictates, along which every image is built up. Though the movement of our eye is discrete in itself, the movement of our "Mind's eye" follows a duplicate course of the line, a principal ray of light moving along with the line of sight. The continuous movement of our "Mind's eye" triggers the notion of intricacy.