According to some scholars, Thomas Hobbes articulated the concept of the social contract. Keep in mind that Hobbes lived in the period sometimes referred to as the Enlightenment which was characterized by a declining influence of the church. He argued that people are egotistic, distrustful of others, and prone to competition. As a result, the social contract is needed to assuage conflict between persons and also between nations.

Rousseau, who lived in the period leading up to the French Revolution,  argued that conflict and war was a consequence of “unnatural” social organization, which included examples such as private property, monogamy, and "civil" society. You should recognize similarities with aspects of the conflict paradigm here.​

Malthus was particularly concerned with the consequences of unchecked population. Competition over scarce resources could result in war.
NOTE: While there is much debate, a number of leading figures in foreign policy suggest that future wars will likely result from food and water shortages. It would not be a mistake to view aspects of his thoughts through the lens of the functionalist paradigm as, in his view, excessive population growth was very disruptive of the social order.​