Henry George Atkinson (c.1812–c.1890), a free thinker and supporter of naturalism, published extensively on phrenology, mesmerism, and spiritualism. He became acquainted with the professional writer, political activist and radical philosopher Harriet Martineau (1802–76) in the 1840s, when she attributed her recovery from a long illness to mesmerism. Their correspondence was published in 1851, and promotes a radical form of atheistic naturalism, more extreme than that found in George Combe's best-selling Constitution of Man (also published in this series). It ranges widely over topics including the brain and the nervous system, matter and causation, superstition, theology and science. The book promotes the purity of natural law as superior to social customs and institutions, and reflects many concerns of the intelligentsia of the time, amongst whom it stirred up much controversy.