Thomas Hobbes (1588-1683) on the other hand, redefined the concept of human nature by challenging Aristotle's classical view of human nature as an idealistic perception of humans controlling their desire through reason, being at the same time moral and social animals by nature. According to Hobbes, the human being is neither moral nor social, but possesses: “a perpetual and restless desire for power after power, which ceases only at death” (Hobbes 2009, XI 2). With the inevitable and constant struggle for power, Hobbes helped conceptualize human nature, which became central to realism. Hobbes characterizes human nature as selfish within the state of nature and introduces social contract theory so that man can survive in anarchy. Singh also explains how one of the most significant political philosophers, Thomas Hobbes, considered the principle of the universe to be made up of particles that move according to a mechanical law. Consequently, Hobbes did not perceive man as a social or political animal, but perceived him as a microcosm and the essence of the universe. Man in this view is considered to be guided by his senses, since memory and imagination all derive from the senses, which means that every man is individual, therefore every man becomes a self-centered creature (Singh 1993, 256). Reasoning, on the other hand, is perceived as artificial and passions as natural. Man is therefore not by nature a reasonable creature and coexistence with other men will hardly be able to satisfy man's desires. Consequently, man possesses a 'conatus', an instinct for self-preservation and an inclination to survive (Hobbes 2007). Men constantly seek honor and dignity, which leads to envy and hatred. Consequently, man lives in perpetual conflict... between paper... and Rousseau." History of Philosophy Quarterly (University of Illinois Press on behalf of North American Philosophical Publications) 2, no. 2 (April 2007): 147–168. “Realism, Neorealism, and American Liberalism.” The Review of Politics (Cambridge University Press) 54, no. 2 (1992): 281–301 historical." The Indian Journal of Political Science 54, no. 2 (1993): 251-272. Strauss, Leo. Thoughts on Machiavelli. Chicago: University of Chicago, 1978. Thucydides. "History of the Peloponnesian War." Internet Archive. Edited by Charles Forster Smith. 1956. http://archive.org/stream/thucydideswithen01thucuoft/thucydideswithen01thucuoft_djvu.txt.Yankelovich, Daniel. “The Idea of ​​Human Ntaure.” Social Research, Human Nature : A Reevoulution (The New School) 40, no. 3 (1973): 407-428.