Kalos kagathos of which kalokagathia  is the derived noun, is a phrase used by classical Greek

Ancient Greece

Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 writers to describe an ideal of personal conduct, especially in a military context. Its use is attested since Herodotus

Herodotus

Herodotus was an ancient Greek historian who was born in Halicarnassus, Caria and lived in the 5th century BC . He has been called the "Father of History", and was the first historian known to collect his materials systematically, test their accuracy to a certain extent and arrange them in a...

 and the classical period. The phrase is adjectival, composed of two adjectives, ("beautiful") and ("good" or "virtuous"), the second of which is combined by crasis

Crasis

Crasis is a type of contraction in which two vowels or diphthongs merge into one new vowel or diphthong — making one word out of two. Crasis occurs in Portuguese and Arabic as well as in Ancient Greek, where it was first described.-French:...

 with καί "and" to form . Werner Jaeger

Werner Jaeger

Werner Wilhelm Jaeger was a classicist of the 20th century.Jaeger was born in Lobberich, Rhenish Prussia. He attended school at Lobberich and at the Gymnasium Thomaeum in Kempen Jaeger studied at the University of Marburg and University of Berlin. He received a Ph.D...

 summarizes it as ”the chivalrous

Chivalry

Chivalry is a term related to the medieval institution of knighthood which has an aristocratic military origin of individual training and service to others. Chivalry was also the term used to refer to a group of mounted men-at-arms as well as to martial valour...

 ideal of the complete human personality, harmonious in mind and body, foursquare in battle and speech, song and action”.

Uses

The phrase could be used both in a generic sense, or with certain specific force. As a generic term, it may have been used as the combination of distinct virtues, which we might translate as "handsome and brave", or the intersection of the two words "good" or "upstanding". Translations such as "gentleman" or "knight" have traditionally been suggested to convey the social aspect of the phrase, while "war hero" or the more cynical "martyr" are more recent versions, and emphasise the military element.

It became a fixed phrase by which the Athenian aristocracy referred to itself; in the ethical philosophers, the first of whom were Athenian gentlemen, the term came to mean the ideal or perfect man.

The possession of the beautiful and the good ("kalos kai agathos") has a correspondent in Latin: "mens sana in corpore sano

Mens sana in corpore sano

Mens sana in corpore sano is a famous Latin quotation, often translated as "A sound mind in a sound body." There is also a sports equipment company with a name based on a twist of this quotation...

" (healthy soul in healthy body). It is also seen as a target in balanced education of body and spirit.

There is thematic discussion of kalokagathia in Aristotle

Aristotle

Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

's Eudemian Ethics

Eudemian Ethics

The Eudemian Ethics is a work of philosophy by Aristotle. Its primary focus is on Ethics, making it one of the primary sources available for study of Aristotelian Ethics. It is named for Eudemus of Rhodes, a pupil of Aristotle who may also have had a hand in editing the final work...

 Book VIII, chapter 3. And how a kaloskagathos (gentleman) should live is also discussed at length in Xenophon

Xenophon

Xenophon , son of Gryllus, of the deme Erchia of Athens, also known as Xenophon of Athens, was a Greek historian, soldier, mercenary, philosopher and a contemporary and admirer of Socrates...

's Socratic dialogues, especially the Oeconomicus.

Kalos

The adjective καλός means beautiful and encompasses meanings equivalent to English "good", "noble", and "handsome". The form given by convention is the masculine, but it was equally used of women (the feminine form is καλή) and could also describe animals or inanimate objects.

Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

, in his work Republic

Republic (Plato)

The Republic is a Socratic dialogue written by Plato around 380 BC concerning the definition of justice and the order and character of the just city-state and the just man...

, used the term τό καλόν (the neutral form) in his attempts to define ideals. However, his protagonist in the dialogue, Socrates

Socrates

Socrates was a classical Greek Athenian philosopher. Credited as one of the founders of Western philosophy, he is an enigmatic figure known chiefly through the accounts of later classical writers, especially the writings of his students Plato and Xenophon, and the plays of his contemporary ...

, stated that he did not fully comprehend the nature of this καλόν.

Agathos

This second adjective means good and had no particular physical or aesthetic connotations, but could describe a person's excellence of character (ethical virtue) for example their bravery. Again, around the 4th century, it had become politically meaningful, and carried implications of dutiful citizenship.