19th-century philosophy of complexity from mathematics, astronomy, physics, chemistry, biology, and a new discipline called "sociology", which is the study of the "dynamics and statics of society". The American philosophers Charles Sanders Peirce and William James developed the pragmatist philosophy in the late 19th century. The twilight years of the 19th century in Britain saw the rise of British idealism, a revival of interest in the works of Kant and Hegel. Transcendentalism was rooted in Immanuel Kant's transcendence and German idealism, led by Ralph Waldo Emerson and Henry David Thoreau. The main belief was in an ideal spiritual state that 'transcends' the
History of slavery in the Muslim world up until the 19th century. Livingstone and Stanley were then the first Europeans to penetrate to the interior of the Congo basin and to discover the scale of slavery there. The Arab Tippu Tib extended his influence and made many people slaves. After Europeans had settled in the Gulf of Guinea, the trans-Saharan slave trade became less important. In Zanzibar, slavery was abolished late, in 1897, under Sultan Hamoud bin Mohammed. The rest of Africa had no direct contact with Muslim slave-traders. While slaves were sometimes employed for manual labour during the Arab slave trade, this was usually the exception