According to Maimonides, a tzadik is "one whose merit surpasses [his/her] iniquity", and every person can reach the level of a Tzadik. According to the Tanya, a tzadik has no evil inclination, and only a select few predestined to attain this level can attain it. According to Kabbalah (and particularly the Hasidic understanding of Kabbalah), the world is sustained on the "shoulders" of Tzadikim Nistarim, divinely predestined exceptionally righteous people in a generation. Nobody has knowledge about who was such a tzaddik, even one of these exceptionally righteous people would not know that they really are such a tzadik. These people are understood to have perfected their personal service of God to such an extent that they become literally and physically aware of God. These righteous people's perception (of both spiritual and physical, not to mention temporal matters) transcends the apparent boundaries of existence.