Kindness is a virtue in many cultures and religions. The above picture is from a Laotian temple, depicting the parable of Buddha and the elephant Nalagiri. Devadutta, jealous of Buddha and wanting to hurt him, sends an angry elephant named Nalagiri into a street where Buddha and his colleagues were walking. As the angry Nalagiri approached them, Buddha's loving kindness and friendliness tames Nalagiri. The parable suggests kindness affects everyone. Buddhists call such kindness in virtuous state of perfection as Mettā, while some Indian literature refer to it as maitrī (Sanskrit: मैत्री).
Kindness is a behavior marked by ethical characteristics, a pleasant disposition, and concern for others. It is known as a virtue, and recognized as a value in many cultures and religions (see ethics in religion). Research has shown that acts of kindness does not only benefit receivers of the kind act, but also the giver, as a result of the release of neurotransmitters responsible for feelings of contentment and relaxation when such acts are committed. 
According to Book Two of Aristotle's "Rhetoric" it is defined as virtue). It is defined as being "helpfulness towards some one in need, not in return for anything, nor for the advantage of the helper himself, but for that of the person helped".[dead link]
Philosopher Friedrich Nietzsche argued that kindness and love are the "most curative herbs and agents in human intercourse".
In 2009, analysts warned that 'real kindness changes people in the doing of it, often in unpredictable ways. Real kindness is an exchange with essentially unpredictable consequences'.
They also argue that, in a relationship, 'real kindness, real fellow-feeling, entails hating and being hated - that is, really feeling available frustrations – and through this coming to a more real relationship'.
It has been suggested that 'most of Shakespeare's opus could be considered a study of human kindness'.
Robert Louis Stevenson considered that 'the essence of love is kindness; and indeed it may best be defined as passionate kindness: kindness, so to speak, run mad and become importunate and violent'.
The Christian apostle Paul lists kindness as one of the nine traits considered to be the "fruit of the Spirit"  in Galatians 5:22.
^Aristotle (translated by Lee Honeycutt). "Kindness". Rhetoric, book 2, chapter 7. Retrieved 2005-11-22.
^Nietzsche, Friedrich Wilhelm. "On the History of Moral Feelings," Human, all too human: a book for free spirits. Aphorism 48. [Original: Menschliches, Allzumenschiles, 1878.] Trans. Marion Faber with Stephen Lehman. University of Nebraska Press: First Printing, Bison Books, 1996.
^Adam Phillips & Barbara Taylor, On Kindness (London 2009) p. 12