Both physiological differences between men and women and what we would consider culturally constructed ideas about masculinity and femininity were thought to be products of nature. As such, they were the given constraints within which human lives were bounded. But nature was not always immutable. The practice of creating eunuchs allowed humans to modify the physical development of the male body. The supposedly natural inclinations and cognitive proclivities of men and women were open to manipulation through ethical effort or training. Medieval Roman conceptions of gender were formed, on the one hand, by a set of beliefs about male and female human nature, and on the other, by the conviction that humans had moral agency to modify their performance of their gender for good or ill. Nature dealt each human a hand at birth by endowing him with a male body and a proclivity toward steadfastness or her with a female body and a proclivity toward fickleness (for example). Yet those humans were not helplessly bound to live out those dispositions in their lives. Medieval Roman texts abound with stories of women overcoming their natural weaknesses and men whose vices make them unnaturally weak. Stories of female ascetics who so far conquered their nature that they passed as male monks were perennially popular and witnessed to a measure of human control even over the manifestation of physiological aspects of gender. The bonds of nature were powerful and the hand one was dealt at birth was clearly the central determinant of one's life path. Nevertheless, belief in the power of human moral agency made the performance of gender by Medieval Romans much more than merely a matter of doing what came naturally.

To understand Medieval Roman gender, therefore, we need to establish what they thought was given by nature, what was open to human manipulation, and the ideal moral and physical gender virtues to which they strove. This chapter takes on nature and its manipulation: what Medieval Roman people believed to be natural about the physical differences between male and female bodies, and about male and female spiritual and mental proclivities and inclinations, as well as conceptions of the processes of moral and ethical formation. This background will set us up to understand gender ideals in the following chapter.