 In July 1916, Lenin's mother died, but he was unable to attend her funeral.Her death deeply affected him, and he became depressed, fearing that he too would die before seeing the proletarian revolution.In September 1917, Lenin published "Imperialism, the Highest Stage of Capitalism", which argued that imperialism was a product of monopoly capitalism, as capitalists sought to increase their profits by extending into new territories where wages were lower and raw materials cheaper.