Paul Sérieux was born in Le Havre on 4 July 1864.
[citation needed] Sérieux is best known for research of psychoses and delusional thought processes, and his collaborative work with Joseph Capgras (1873–1950).
Sérieux was also instrumental in introducing the theories of German psychiatrist Emil Kraepelin (1856–1926) into French psychiatry.
[1] With his one-time mentor Valentin Magnan (1835–1916), he co-authored the book Le délire chronique a evolution systématique (1892), and in 1909 with Capgras, he published a treatise called Les folies raisonnantes.
Sérieux traveled widely throughout Europe, and created an extensive report on the state and conditions of psychiatric treatment in French, German, Swiss and Belgian mental asylums.