F1 is one of the most original figures of 19th-century French psychiatry. Educated in literature, he taught philosophy at Lycée Louis le Grand in Paris and went on to defend his thesis in medicine in 1846. His initial training put him on his guard against the fascination for philosophy expressed by many of his alienist contemporaries who sought to address the insufficiencies of early psychological theory. He became a shrewd critic of the subordination of psychology to philosophy and was one of the first to attempt to develop a resolutely objective psychology based on precise clinical observations. Along with his colleague Claude Bernard, the founder of experimental methodology in medicine, he defended a complex conception of mental disorder etiology in which he considered psychology and physiology to be complementary to one another. He was appointed Professor of General Pathology in 1867 and continued to strive toward integrating his work in psychology within a global medical framework.
Charles Lasègue’s manifold achievements were marked by four major contributions. To start with, he distinguished himself in the delineation of precise clinical criteria allowing for differentiation between neurological troubles and symptoms of conversion hysteria. Within international semiology, Lasègue’s sign designates the pain triggered by elongation of the leg, allowing for diagnosis of sciatica. In 1852 he described persecutory delusions and their evolution. In 1873 he described hysterical anorexia, and although this was 5 years after Gull’s description of hysterical apepsia, Lasègue focused intensively on the psychological symptoms, emphasizing the role of parental attitudes and family interactions. Finally, in 1877 he introduced and described with Jules Falret the concept of "folie à deux," fully describing the psychological mechanisms (1). This term continues to be employed to this day in the international psychiatric vocabulary.