Ma'at is the central concept of Egyptian spiritual and ethical life — untranslatable as a single English word because it encompasses truth, justice, cosmic order, balance, harmony and the right relationship between all things. Ma'at is simultaneously a goddess (depicted with an ostrich feather on her head) and the cosmic principle that she embodies — the order that underlies and sustains the universe.
The pharaoh's primary function was to maintain Ma'at — to ensure that the cosmic order was reflected in the social order, that justice prevailed, that the Nile flooded on time, that the agricultural cycle continued, that the stars moved in their proper courses. The failure of Ma'at produced Isfet — chaos, disorder, the dissolution of the cosmic order. Every aspect of Egyptian religious and political life was oriented toward maintaining this fundamental balance.
The weighing of the heart in the Hall of Two Truths — the central scene of the Book of the Dead — encodes Ma'at's importance: at death, the heart is weighed against the feather of Ma'at. A heart heavy with untruth, injustice and transgression fails the test; a heart light with right living and honest dealing passes through to eternal life. This is one of the first documented ethical accountability systems in human history.