Karl Marx (5 May 1818 – 14 March 1883) was a German philosopher, economist, sociologist, historian, journalist, and revolutionary socialist. His ideas played a significant role in the establishment of the social sciences and the development of the socialist movement. He is also considered one of the greatest economists in history. He published numerous books during his lifetime, the most notable being The Communist Manifesto (1848) and Capital (1867 –1894). He worked closely with his friend and fellow revolutionary socialist, Friedrich Engels.