The Animal Mind (1904) was the publication that earned Margaret her well desired fame. Margaret rejected theories proposed by Rene Descartes which state that every human being is a bipartite creature composed by a material body and an immaterial mind, and that these traits are exclusive to humans. Margaret believed the opposite – that animals shared these characteristics. At that time many believed that animals have no consciousness, therefore basically mindless. Margaret suggested that animals possess mental processes and abilities to learn that are structurally similar to those found in humans. "The effects of previous experience are recalled in the guise of an idea or mental image of some sort...The actions of our fellow-men resemble our own, and we therefore infer them like subjective states to ours: the actions of animals represent ours less completely, but difference is one of degree, not of kind...the facts are those of human and animal behavior; but the mental processes are as justifiable inferences as any others with which science deals...We know not where consciousness begins in the animal world. We know where it surely resides in ourselves; we know where it exists beyond a reasonable doubt in those animals of structure resembling ours which rapidly adapt themselves to the lessons of experience...Beyond this point, for all we know, it may exist in simpler and simpler forms until we reach the very lowest of living beings" (Washburn, 1908:539-541-42).
* Washburn, M. F., 1908. The Animal Mind: A Text-Book of Comparative Psychology. New York: Macmillan.