: Understanding the biological functions and anatomical details of both partners.

: The text explored the role of "olfactory sexual impressions" and other sensory stimuli in attraction.

: It offered thorough descriptions of preliminaries (foreplay) and the after-effects of coitus , stressing that the act does not end at climax.

Theodoor Hendrik van de Velde’s (1926) was a groundbreaking scientific treatise that transformed the early 20th-century understanding of marital intimacy. At its core, the book argued that a successful marriage is an art form that requires both scientific knowledge and deliberate technical skill. The Four Pillars of Ideal Marriage

Van de Velde structured his work around four "cornerstones" essential for a harmonious union: