Interpretation of Dreams

Freud’s theories were no doubt influenced by other scientific discoveries of his day. Charles Darwin's understanding of humankind as a progressive element of the animal kingdom certainly informed Freud's investigation of human behavior. Additionally, the formulation of a new principle by scientist Hermann von Helmholtz, stating that energy in any given physical system is always constant, informed Freud's scientific inquiries into the human mind. Freud's work has been both rapturously praised and hotly critiqued, but no one has influenced the science of psychology as intensely as Sigmund Freud.

The great reverence that was later given to Freud's theories was not in evidence for some years. Most of his contemporaries felt that his emphasis on sexuality was either scandalous or overplayed. In 1909, he was invited to give a series of lectures in the United States; it was only after the ensuing publication of his book Five Lectures on Psycho-Analysis (1916) that his fame grew exponentially.