The four Brahmaviharas (the “Four Brahama Abodes”) are products of both the Buddha’s insight into the value of compassion and a testament to the power of the Vedic thought from which Buddhism sprang.

The Buddha, approached by many great Brahmanical minds in his lifetime, found it useful to respond to his questioners using terms they would understand.  The Brahma-Vihara (or Divine Abodes) concept predated the Buddha.  Brahma, the supposed creator of the Vedas and existence, was naturally somebody who many people would like to spend some time with.  In that spirit, there were many searchers who wanted to know what they could do in their earthly lives to eventually be reborn with Brahma.

Buddha’s answer was to practice four mindsets: First comes Metta (or Maitri as known in Sanskrit); this is usually translated as loving-kindness.  Second comes compassion (Karuna in both Pali and Sanskri), third comes empathetic joy (Mudita in both Pali and Sanskrit), and last comes equanimity (Upeksa in Pali, Upekkha in Sanskrit). Loving-kindness is the feeling of a mother toward her child, compassion is the mother’s care for the child when the child is ill, empathetic joy is the mother’s happiness for the child’s successes, and equanimity is the understanding that the child has their own life and might not always be around.1

Perhaps the Buddha understood the significance of the number four to his contemporary Brahmins.  Brahma, as commonly depicted, has four heads.  And from each head, a Veda emerges, comprising the Four Vedas.

In Mahayana parlance, the Buddha presented his ultimate truth in a way that would be understood by the people hearing it.

Pali: Cattāri brahmavihārā
Sanskrit: Catvāri brahmavihārāḥ

1Gethin, 186-187.