The debate on species during the late 1840s and 1850s covered a wide range of topics. The discussion of the probable laws regulating the geographical distribution of organic forms, inquiries into the natural history of mankind, discoveries in embryology and physiology, the accumulation of palaeontological data and broad theological and natural theological considerations were issues acknowledged as relevant to the solution of the species puzzle. Few naturalists were known or suspected to hold transmutationist views. The great majority of participants in the debate acknowledged the inadequacy of available transmutationist mechanisms, though among anthropologists and medical authors both in England and in Europe, forms of transformism were actually upheld.

Interpretation differed widely as to the consequences to be expected from explanations of the succession of beings in natural terms. Some were convinced that the very fact of asking this question implied support for a basically materialistic view of nature. Sedgwick and Hugh Miller were the most outspoken representatives of this opinion. Sedgwick turned successive editions of his 1834 Discourse into an interminable anti-transmutationist manifesto. The fifth edition published in 1850 had a preface of 442 pages containing a detailed criticism of all possible arguments used to support the naturalistic interpretation of the succession of species.

Sedgwick warned that the ideas put forward by the Vestiges, Geoffroy Saint-Hilaire, and ‘other materialists of the same school’ were bound to have disastrous effects on society: materialism, ‘if current in society,… will under mine the whole moral and social fabric, and inevitably will bring discord and deadly mischief.’ Miller was equally convinced that the development theory was not only wrong but dangerous. When intelligent mechanics became materialists, ‘they become turbulent subjects and bad men’.