Erik Erikson, a developmental psychologist, proposed eight life stages through which each person must develop. In order to move on to the next stage, the person must work out a "crisis" in which a new dilemma must be solved. In each stage, they must understand and balance two conflicting forces, and so parents might choose a series of parenting styles that helps each child as appropriate at each stage. The first five of his eight stages occur in childhood: The virtue of "hope" requires balancing trust with mistrust, and typically occurs from birth to one year old. "Will" balances autonomy with shame and doubt around the ages of two to three. "Purpose" balances initiative with guilt around the ages of four to six years. "Competence" balances industry against inferiority around ages seven to 12. "Fidelity" contrasts identity with role confusion, in ages 13 to 19. The remaining adult virtues are love, care and wisdom.