This short conference paper takes a theme from my doctoral research and complements the argument of the dissertation with respect to the fundamental role of Herbert Spencer's ideas in psychology, neuroscience and related disciplines, which was even greater than his under-rated role in the history of evolutionary thinking in general. It was delivered to the Eleventh International Congress of the History of Science, Warsaw, August 1965 and published in Actes du Xle Congres International d'Histoire des Sciences Warsaw: Ossolineum, 1967, vol. 2, pp. 273-78.