Modernism

One of the defining changes occurring at the end of the Middle Ages, is the end of the dominance of Aristotelian philosophy, and its replacement by a new approach to the study of nature, including human nature. In this approach, all attempts at conjecture about formal and final causes was rejected as useless speculation. Also, the term "law of nature" now applies any regular and predictable pattern in nature, not literally a law made by a divine law-maker, and in the same way "human nature" becomes not a special metaphysical cause, but simply whatever can be said to be typical tendencies of humans.

Although this new realism applied to the study of human life from the beginning, for example in Machiavelli's works, the definitive argument for the final rejection of Aristotle was associated especially with Francis Bacon, and then René Descartes, whose new approach returned philosophy or science to its pre-Socratic focus upon non-human things. Thomas Hobbes, then Giambattista Vico, and David Hume all claimed to be the first to properly use a modern Baconian scientific approach to human things.

Hobbes famously followed Descartes in describing humanity as matter in motion, just like machines. He also very influentially described man's natural state (without science and artifice) as one where life would be "solitary, poor, nasty, brutish and short."Following him, John Locke's philosophy of empiricism also saw human nature as a tabula rasa. In this view, the mind is at birth a "blank slate" without rules, so data is added, and rules for processing them are formed solely by our sensory experiences.

Jean Jacques Rousseau pushed the approach of Hobbes to an extreme and criticized it at the same time. He was a contemporary and acquaintance of Hume, writing before the French Revolution and long before Darwin and Freud. He shocked Western Civilization with his Second Discourse by proposing that humans had once been solitary animals, without reason or language or communities, and had developed these things due to accidents of pre-history. (A proposal which was also made, less famously, by Giambattista Vico.) In other words, Rousseau argued that human nature was not only not fixed, but not even approximately fixed compared to what had been assumed before him. Humans are political, and rational, and have language now, but originally they had none of these things. This in turn implied that living under the management of human reason might not be a happy way to live at all, and perhaps there is no ideal way to live. Rousseau is also unusual in the extent to which he took the approach of Hobbes, asserting that primitive humans were not even naturally social. A civilized human is therefore not only imbalanced and unhappy because of the mismatch between civilized life and human nature, but unlike Hobbes, Rousseau also became well known for the suggestion that primitive humans had been happier, "noble savages."

Rousseau's conception of human nature has been seen as the origin of many intellectual and political developments of the 19th and 20th centuries. He was an important influence upon Kant, Hegel, and Marx, and the development of German Idealism, Historicism, and Romanticism.

What human nature did entail, according to Rousseau and the other modernists of the 17th and 18th centuries, were animal-like passions that led humanity to develop language and reasoning, and more complex communities (or communities of any kind according to Rousseau).

In contrast to Rousseau, David Hume was a critic of the oversimplifying and systematic approach of Hobbes and Rousseau and some others whereby, for example, all human nature is assumed to be driven by variations of selfishness. Influenced by Hutcheson and Shaftesbury, he argued against oversimplification. On the one hand he accepted that for many political and economic subjects people could be assumed to be driven by such simple selfishness, and he also wrote of some of the more social aspects of "human nature" as something which could be destroyed, for example if people did not associate in just societies. On the other hand he rejected what he called the "paradox of the sceptics" saying that no politician could have invented words like "'honourable' and 'shameful,' 'lovely' and 'odious,' 'noble' and 'despicable,'" unless there was not some natural "original constitution of the mind."

Hume, like Rousseau, was controversial in his own time for his modernist approach, following the example of Francis Bacon and Thomas Hobbes, of avoiding consideration of metaphysical explanations for any type of cause and effect. He was accused of being an atheist. Concerning human nature also, he wrote for example:
We needn't push our researches so far as to ask 'Why do we have humanity, i.e. a fellow-feeling with others?' It's enough that we experience this as a force in human nature. Our examination of causes must stop somewhere.

After Rousseau and Hume, the nature of philosophy and science changes, branching into different disciplines and approaches, and the study of human nature changes accordingly. Rousseau's proposal that human nature is malleable became a major influence upon international revolutionary movements of various kinds, while Hume's approach has been more typical in Anglo-Saxon countries including the United States.