Karl Marx (German: [ˈkaʁl ˈmaʁks]; 5 May 1818 – 14 March 1883) was a German philosopher, economist, historian, sociologist, political theorist, journalist and socialist revolutionary.

Born in Trier, Germany, Marx studied law and philosophy at university. He married Jenny von Westphalen in 1843. Due to his political publications, Marx became stateless and lived in exile with his wife and children in London for decades, where he continued to develop his thought in collaboration with German thinker Friedrich Engels and publish his writings, researching in the reading room of the British Museum. His best-known titles are the 1848 pamphlet, The Communist Manifesto, and the three-volume Das Kapital. His political and philosophical thought had enormous influence on subsequent intellectual, economic and political history, and his name has been used as an adjective, a noun and a school of social theory.

Marx's critical theories about society, economics and politics – collectively understood as Marxism – hold that human societies develop through class struggle. In capitalism, this manifests itself in the conflict between the ruling classes (known as the bourgeoisie) that control the means of production and the working classes (known as the proletariat) that enable these means by selling their labour power in return for wages. Employing a critical approach known as historical materialism, Marx predicted that, like previous socio-economic systems, capitalism produced internal tensions which would lead to its self-destruction and replacement by a new system: socialism. For Marx, class antagonisms under capitalism, owing in part to its instability and crisis-prone nature, would eventuate the working class' development of class consciousness, leading to their conquest of political power and eventually the establishment of a classless, communist society constituted by a free association of producers. Marx actively pressed for its implementation, arguing that the working class should carry out organised revolutionary action to topple capitalism and bring about socio-economic emancipation.

Marx has been described as one of the most influential figures in human history, and his work has been both lauded and criticised. His work in economics laid the basis for much of the current understanding of labour and its relation to capital, and subsequent economic thought. Many intellectuals, labour unions, artists and political parties worldwide have been influenced by Marx's work, with many modifying or adapting his ideas. Marx is typically cited as one of the principal architects of modern social science.

Jean-Jacques Rousseau (UK: , US: ; French: [ʒɑ̃ˈʒak ʁuˈso]; 28 June 1712 – 2 July 1778) was a Genevan philosopher, writer and composer. His political philosophy influenced the progress of the Enlightenment throughout Europe, as well as aspects of the French Revolution and the development of modern political, economic and educational thought.

His Discourse on Inequality and The Social Contract are cornerstones in modern political and social thought. Rousseau's sentimental novel Julie, or the New Heloise (1761) was important to the development of preromanticism and romanticism in fiction. His Emile, or On Education (1762) is an educational treatise on the place of the individual in society. Rousseau's autobiographical writings—the posthumously published Confessions (composed in 1769), which initiated the modern autobiography, and the unfinished Reveries of a Solitary Walker (composed 1776–1778)—exemplified the late-18th-century "Age of Sensibility", and featured an increased focus on subjectivity and introspection that later characterized modern writing.

Rousseau befriended fellow philosophy writer Denis Diderot in 1742, and would later write about Diderot's romantic troubles in his Confessions. During the period of the French Revolution, Rousseau was the most popular of the philosophers among members of the Jacobin Club. He was interred as a national hero in the Panthéon in Paris, in 1794, 16 years after his death.