The Annunciation. One conception was simultaneously central and exceptional in Western culture: that of Jesus Christ. The Archangel Gabriel was believed to have revealed to the Virgin Mary that she would conceive through the Holy Spirit. The iconographical tradition of ‘the Annunciation’ built upon numerous theological writings, but primarily the Gospel according to Luke. In this fifteenth-century fresco from Western Croatia, the naked baby Jesus, carrying a wooden cross on his shoulder, plunges towards Mary from the mouth of God the Father. The Virgin is shown with a book (‘she was always engaged in prayer and in searching the law’, Pseudo-Matthew, 1: 3). Gabriel is holding a scroll with the words ‘Hail [Mary], full of grace’ (Luke 1:28).

Acquiring a soul

Aristotle’s arguments, that the formation of a new being was gradual and the soul acquired some time after conception, informed medieval ideas.

The ancient Greek philosopher Aristotle argued that the female provided the menstrual blood as the passive material from which the active male semen generated the new form. While observing chick eggs at different stages, he became convinced that the form gradually emerged from unformed matter in a process he named ‘epigenesis’. Epigenesis required a soul. All organisms had a vegetative soul, and animals also a locomotor one, but the rational soul was reserved for humans. Aristotle drew on humoralism, which postulated that physical and mental features are determined by an innate balance of qualities such as heat, coldness, moisture and dryness. The hotter male embryos were ensouled around the fortieth day of pregnancy while the cooler females took twice as long.

For Christians, the soul had a different meaning and purpose. Some theologians placed ensoulment, or the acquisition of a God-given immortal soul, at conception. Yet from the late Middle Ages the Aristotelian view dominated. For practical purposes, quickening tended to be interpreted as coinciding with the entry of the soul. Understanding the early embryo as not-yet-human contributed to widespread tolerance of abortion. This would begin to change only in the Enlightenment

Early-modern images of Aristotelian epigenesis, 1554   The moment of ensoulment, 1400s