The way in which medieval canonists and theologians commonly explained the innate difference between men and women might seem quite strange today. Most writers associated men with heat and women with coldness, and they used this defining factor to justify both physical and psychological discrepancies between the two sexes. According to Giles of Rome, "heat is the sperm's essential quality," and another common perception held that heat within the womb of a mother-to-be created a male child, while absence of it led to the birth of a girl (Salisbury, 91). The heat of the male was what supposedly created great sexual desire in females, as illustrated below by a passage from the late medieval medical tract Secrets of Women, and many believed that through intercourse, a woman gained the vital heat that she lacked (Salisbury, 90):
The more women have sexual intercourse, the stronger they become, because they are made hot by the motion that the man makes during coitus. Further, male sperm is hot because it is of the same nature as air and when it is received by the woman it warms her entire body, so women are strengthened by this heat.
It is apparent from this passage that female "coldness" was considered a negative quality, whereas the heat associated with men was perceived as beneficial. Accordingly, Secrets of Women also argues that "woman has a greater desire for coitus than a man, for something foul is drawn to the good" (Salisbury, 93).
Using this theory of heat and coldness, authors and physicians alike explained not only these differences in sexual desire, but physical differences between men and women as well. Women's "pear-shaped" physiques were seen as a result of their natural coldness, which allowed their nutrients to pass into the lower parts of their bodies before settling and being processed. Conversely, men's extreme heat created a broader upper body and a slender waist and hips because their food was processed before it could travel down towards the lower regions of the body (Brundage, 426). Joan Cadden clearly sums up the universality of this rationale in Meanings of Sex Differences in the Middle Ages when she notes that "[heat] was one of the most fundamental factors in the distinction between females and males. It had a place in pharmacology, astrology, and ideas about the production of semen. It operated as a basis for the conceptualization of the masculine and the feminine both within and beyond reproduction" (Salisbury, 91).
(A.M.S.) Brundage, James A. Law, Sex, and Christian Society in Medieval Europe. Chicago: The University of Chicago Press, 1987.
Salibury, Joyce. E. "Gendered Sexuality." Handbook of Medieval Sexuality. Vern L. Bullough and James A. Brundage, eds. New York: Garland, 1996, pp. 81-102.