“Self-Fulfilling Prophecy: A concept introduced into sociology by Robert Merton (see his Social Theory and Social Structure, 1957), and allied to William Isaac Thomas’s earlier and famous theorem that ‘when people define situations as real, they become real in their consequences.’ Merton suggests the self-fulfilling prophecy is an important and basic process in society, arguing that ‘in the beginning, a false definition of the situation evokes a new behavior which makes the original false conception come true. [It] perpetuates a reign of error.’”
Excerpted from: Marshall, Gordon, ed. Oxford Dictionary of Sociology. New York: Oxford University Press, 1994.