The ancient Greek word for good first meant brave and capable
In early Greek, agathos described someone good at things, brave and competent, while kakos meant bad or cowardly. Only around 400 BC, with Democritus and then Plato, did the words take on an absolute moral sense. Even ethics and morality began as words for local custom.
Every known language has words for desirable and undesirable, and judging right from wrong appears to be a cultural universal. What varies is the shape of the contrast. Zoroaster reduced the early Iranian pantheon to two warring powers, Ahura Mazda, illuminating wisdom, and Angra Mainyu, destructive spirit. Egypt opposed Ma'at, the principle of order and justice, to Isfet, chaos and decay, and Mesopotamian myth pitted Marduk against Tiamat.
Not every tradition frames it as a cosmic duel. Confucianism has no direct equivalent; its concern is proper social relationships, so evil amounts to wrong conduct. Pyrrhonist sceptics held that good and evil are not in things themselves but relative to whoever judges. Spinoza, writing in a quasi-mathematical style, defined good as what we know to be useful and argued that knowledge of evil is inadequate knowledge, so a mind with only adequate ideas would form no notion of evil at all.
Religions answer differently again. Augustine of Hippo defined sin as a word, deed or desire against God's eternal law. The Baháʼí Faith denies that evil truly exists, treating it as an absence of good in the way cold is an absence of heat; `Abdu'l-Bahá observed that a scorpion is evil only relative to people, since its sting is its defence. For the Abrahamic faiths, explaining where evil comes from has always been a hard problem.
Modern thinkers moved the question into psychology. Nietzsche, rejecting Judeo-Christian morality in two books including Beyond Good and Evil, argued that the resentment of the weak toward their masters turned the merely non-good into the religious idea of evil. Carl Jung described people projecting their own shadow onto others so that evil seems external. In 2007 Philip Zimbardo, drawing on his Stanford prison experiment, proposed in The Lucifer Effect that collective identity can lead ordinary people into evil acts.
Source: Good and evil
