A Critical Examination of the Position of Mr. Darwin's Work, "On the Origin of Species," in Relation to the Complete Theory of the Causes of the Phenomena of Organic Nature / Lecture VI. (of VI.), "Lectures to Working Men", at the Museum of Practical Geology, 1863, on Darwin's Work: "Origin of Species"

The lecturer critically assesses Darwin's account of how species change, separating the distinct problems of the first appearance of life from the later modification and perpetuation of organisms, and arguing that Darwin legitimately confines his inquiry to the latter. He sets out a clear method for scientific hypotheses—establishing that proposed causes exist, are sufficient to produce the observed phenomena, and exclude other known causes—and applies these tests to Darwin's idea that variability and inherited tendencies interacting with environmental conditions account for organic diversity. The lecture balances defense of methodological limits with close scrutiny of evidential and logical support for evolutionary explanation.