A self-fulfilling prophecy is a preiction that directly or indirectly causes itself to become true. Although examples of such prophecies can be found in literature as far back as ancient Greece and ancient India, it is 20th-century sociologist Robert K. Merton who is credited with coining the expression "self-fulfilling prophecy" and formalizing its structure and consequences. In his book Social Theory and Social Structure, Merton gives as a feature of the self-fulfilling prophecy: