Perhaps the chief antagonist in the eighteenth century of the social contract theory was David Hume (1711–1776), the father of social psychology. According to Hume, the origin of society was not in a contract arrived at by intellectual processes; it was instinctive. Man is a social animal. At the basis of this sociability lies the sex instinct, which resulted in the establishment of the family. The sex instinct is strongly supported by the sentiment of sympathy, which also is innate, and which may develop into intelligent co-operation. Man is not entirely self-centered; he takes pleasure in other people’s pleasures and suffers when others are in pain, or the victims of disease, or are dying. Sympathy, like the sex instinct, is a genuinely fundamental element in human nature and in society. However, the combination of sympathy and the sex instinct is not strong enough to support the family in either its simple or complex stages from the attacks upon it that are made by inherent human selfishness. Hence, social and political organizations are necessary to hold the selfish impulses and interests of mankind in check. Intellectual control of society thus becomes necessary and consciously recognized. Environment alone does not cause people in a given community to act alike. It is imitation, primarily, which operates to bring about group conformity.[XI-14] Man in a large measure is governed by interest. It is impossible for men to consult their interests “in so effective a manner as by a universal and inflexible observance of the rules of justice, by which alone they can preserve society, and keep themselves from falling into that wretched and savage condition, which is commonly represented as the state of nature.”[XI-15] According to the contract theory, people expect protection and security. If they meet with tyranny and oppression, they are freed from their promises and return to that state of liberty which proceeded the institution of government. But Hume maintained that if people entered into no contract and made no promises, government would still be necessary in all civilized societies. The obligation of submission to government is not derived from any promise of the subjects.[XI-16] Adam Ferguson (1723–1816) wrote an _Essay on the History of Civil Society_ and _The History of the Progress and Termination of the Roman Republic_. He argued that social institutions and social convenience lead to inherent sociability, and pointed out that competition and conflict are vital to social development. Thomas Paine (1737–1809) asserted that man is inherently social and that social organization is a natural development.