Only science, exact science about human nature itself, and the most sincere approach to it by the aid of the omnipotent scientific method, will deliver man from his present gloom, and will purge him from his contemporary shame in the sphere of interhuman relations.

Translated by Stephen G. Brush, Lectures on Conditioned Reflexes, Preface to the First Russian Edition (p. 41), University of California Press. 1964