Man ordinarily is a robot. He lives apparently awake, but not really. He walks, he talks, he acts, but it is all as if in sleep - not conscious of what he is doing, not conscious of what he is saying, not conscious of all that surrounds him. He moves surrounded in a dark cloud of unawareness. According to Gautama the Buddha, this is the original sin: to live unconsciously, to act out of unconsciousness. In fact, the word 'sin' comes from a root which means forgetfulness. Sin simply means that we are not conscious, aware, alert, that we don't have any inner light to guide us.
