The four brahmavihāras are loving-kindness (mettā), compassion (karuṇā), appreciative joy (muditā), and equanimity (upekkhā). They are called divine or sublime abidings because a mind established in them becomes vast, free from narrow hostility and partiality. Practice extends each quality in all directions to all kinds of beings without enmity.
Mettā wishes for beings to be happy and secure. It is not romantic attachment, approval of every deed, or a demand to feel warm emotion on command. Compassion meets suffering with the wish that it end. It differs from pity, which looks down, and from despair, which collapses under pain. Appreciative joy delights in others' goodness and good fortune, countering envy. Equanimity understands that beings inherit their actions and that not everything lies within one's control; it balances care with wisdom rather than indifference.
The Karaṇīya Mettā Sutta (Kp 9) begins with conduct: be upright, gentle, humble, content, and easy to support; do nothing the wise would blame. Only then does it unfold the boundless wish for all beings. The famous mother-and-only-child simile describes the intensity with which a limitless heart is protected and maintained.
A traditional meditation begins with a being toward whom goodwill comes naturally, then oneself, a benefactor or friend, a neutral person, a difficult person, and finally all beings. Sequences vary by tradition. If directing phrases toward a harmful person causes fear or confusion, do not force intimacy. Establish safety, begin elsewhere, and remember that goodwill can wish for someone to stop harming and face wise restraint.
The Simile of the Saw (MN 21) extends the training to its furthest edge: hatred is not made skillful by another's cruelty. This is a direction of cultivation, not a demand that beginners deny their actual state. First know ill will honestly; then stop feeding it and cultivate the opposite in workable steps.
The discourse moves from personal virtues to a wish that every being—seen and unseen, near and far, born and yet to be born—be happy. It compares protecting this boundless intention to a mother protecting her only child with her life.
The Buddha describes a practitioner pervading every direction with loving-kindness, compassion, appreciative joy, and equanimity—abundant, expansive, limitless, free of hostility and ill will—like a strong conch blast heard in all directions.