Developed by Abraham Maslow in the 60s. Basic needs are at the bottom, and must be satiated before moving on. The needs concerned with our highest potential are at the top. Though sometimes discredited today, it's still referred to in many debates and discussions. Thus, I synopsize it here:

    The Needs:
  1. Physiological Biological needs for oxygen, food, water, and a comfortable body temperature. These needs are the strongest because if deprived, the person would die.
  2. Safety Fairly self-evident. In affluent societies most adults don't have obvious security needs, but children may display these needs.
  3. Love / Affection / Belongingness Possibly many Everythingians are here and achieve some measure of satisfaction from the Everything community?
  4. Esteem Self-respect and respect from others. A sense of worth.
  5. Self-actualization Devotion to a calling, being able to focus outside the self.
It's usually drawn in a pyramid, with (1) at the broad base and (5) at the apex. Please imagine it.