Simplicity is the state or quality of being simple. It usually relates to the burden which a thing puts on someone trying to explain or understand it. Something which is easy to understand or explain is simple, in contrast to something complicated. Alternatively, as Herbert A. Simon suggested, something is simple or complex depending on the way we choose to describe it.

In some uses, simplicity can be used to imply beauty, purity, or clarity. Simplicity may also be used in a negative connotation to denote a deficit or insufficiency of nuance or complexity of a thing, relative to what is supposed to be required.

The concept of simplicity has been related to truth in the field of epistemology. According to Occam's razor, all other things being equal, the simplest theory is the most likely to be true. In the context of human lifestyle, simplicity can denote freedom from hardship, effort or confusion. Specifically, it can refer to a simple living lifestyle.

Simplicity is a theme in the Christian religion. According to St. Thomas Aquinas, God is infinitely simple. The Roman Catholic and Anglican religious orders of Franciscans also strive after simplicity. Members of the Religious Society of Friends (Quakers) practice the Testimony of Simplicity, which is the simplifying of one's life in order to focus on things that are most important and disregard or avoid things that are least important.

In the philosophy of science, simplicity is a meta-scientific criterion by which to evaluate competing theories. In this field, a distinction is often made between two senses of simplicity: syntactic simplicity (the number and complexity of hypotheses), and ontological simplicity (the number and complexity of things postulated). These two aspects of simplicity are often referred to as elegance and parsimony respectively.

Famous quotes containing the word simplicity:

    Both Socrates and Jesus were outstanding teachers; both of them urged and practiced great simplicity of life; both were regarded as traitors to the religion of their community; neither of them wrote anything; both of them were executed; and both have become the subject of traditions that are difficult or impossible to harmonize.
    Jaroslav Pelikan (b. 1932)

    The earliest instinct of the child, and the ripest experience of age, unite in affirming simplicity to be the truest and profoundest part for man. Likewise this simplicity is so universal and all-containing as a rule for human life, that the subtlest bad man, and the purest good man, as well as the profoundest wise man, do all alike present it on that side which they socially turn to the inquisitive and unscrupulous world.
    Herman Melville (1819–1891)

    How truly does this journal contain my real and undisguised thoughts—I always write it according to the humour I am in, and if a stranger was to think it worth reading, how capricious—insolent & whimsical I must appear!—one moment flighty and half mad,—the next sad and melancholy. No matter! Its truth and simplicity are its sole recommendations.
    Frances Burney (1752–1840)