The economic theories developed by Adam Smith (1723-1790) and Thomas Robert Malthus (1766-1834) provided rational explanations for social developments in the Industrial Revolution. Like the philosophs of the Enlightenment, both Smith and Malthus used reason to postulate abstract theories on aspects of society such as economics and population. By examining the emerging factory system, Smith postulated two primary economic theories, the division of labor and the principle of laissez faire (free enterprise). Both of which were based on the capitalist principle. He believed that capitalists, without the interference of government, could be most productive by dividing the production process into many discrete steps. If such measures were implemented, society would naturally progress favorably as more goods were readily available to the public. On the other hand, Malthus reasoned that society was doomed to destruction because over population would deplete a limited food supply. He argued, "Population growth was the true reason for the poverty of the poor." (Sources of the Western Tradition, p. 132) While preventive measures could be instituted, these "difficulties" would halt progress. Therefore, while Robert Malthus and Adam Smith both employ reason in their analysis of society, their conclusions about social progress radically oppose each other, yet still stem from the Enlightenment ideal.
During the Enlightenment, the notion of social progress was first defined and applied by the philosophs. Progress was the use of rational reason to achieve freedom and liberty. This view was expressed to varying degrees in the works of Thomas Jefferson, Locke, Rousseau, and Kant. Of these social philosophers perhaps Kant (1724-1804) summarizes the premise of the Enlightenment most concisely as "man's leaving his self-cased immaturity." (Sources of Western Tradition, p. 55) To Kant, immaturity was "the incapacity to use one's intelligence without the guidance of another.