In Buddhism, one of the Ten Perfections (Paramitas) is Mettā, which is usually translated into English as "loving-kindness". Tenzin Gyatso, 14th Dalai Lama wrote "my religion is kindness" and authored a book entitled Kindness, Clarity, and Insight.
Confucius urges his followers to "recompense kindness with kindness."
According to book two of Aristotle's Rhetoric it is one of the emotions (see list of emotions), which 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.
In a study of 37 cultures around the world, 16000 subjects were asked about their most desired traits in a mate. For both sexes, the first preference was kindness (the second was intelligence).
Philosopher Friedrich Nietzsche had this to say about kindness:
Islamic view of kindness:
"Kindness is half of life.", Imam Musa Al-Kadhim, the 7th Imam of Shia Islam school of thought, Imam Musa Al-Kadhim was the 7th leader after prophet Mohammed as per the beliefs of Shia Muslims.