Vol.:(0123456789) Journal of the History of Biology https://doi.org/10.1007/s10739-019-09577-2 1 3 ORIGINAL RESEARCH Conwy Lloyd Morgan, Methodology, and the Origins of Comparative Psychology Evan Arnet 1 © Springer Nature B.V. 2019 Abstract The British biologist, philosopher, and psychologist Conwy Lloyd Morgan is widely regarded as one of the founders of comparative psychology. He is especially well known for his eponymous canon, which aimed to provide a rule for the interpreta- tion of mind from behavior. Emphasizing the importance of the context in which Morgan was working—one in which casual observations of animal behavior could be found in Nature magazine every week and psychology itself was fghting for sci- entifc legitimacy—I provide an account of Morgan’s vision for the comparative psychologist qua professional psychologist. To this end, I explore the important con- nection between Morgan and the evolutionary theorist, philosopher, and psycholo- gist Herbert Spencer. It is from Spencer, I contend, that Morgan inherited a number of his key epistemological and methodological concerns about the nascent science of comparative psychology. This extends all the way to the canon, which only works as intended when paired with a Spencerian understanding of mental evolution as a progressive linear sequence. Far from being an incidental residue of a pre-Darwin- ian time, hierarchy was intentionally built into the very core of Morgan’s scientifc comparative psychology. Keywords Morgan’s canon · Spencer · Weismann · Comparative psychology Introduction Conwy Lloyd Morgan was a British geologist, psychologist, biologist, philoso- pher, and comparative psychologist who is largely famous for a single sentence: his “canon” of interpretation. Initially presented in a lecture by Lloyd Morgan in England in 1892 (see the report by Dixon 1892), the canon achieved wide circula- tion after its publication in Morgan’s Introduction to Comparative Psychology. As * Evan Arnet earnet@indiana.edu 1 Indiana University Bloomington, 308 Morrison Hall, 1165 E 3rd St, Bloomington, IN 47405, USA