Theories of Breath
Theories of Breathing: Aristotle believed that the principal function of breathing was to cool the body; the nature of animals requires cooling owing to the fiery nature of the soul, which exists in the heart. It achieves this cooling by breathing. In the second century AD, Galen argued that the function of breathing was twofold; to cool the body, and to assist the infusion of vital spirits to the arterial blood. Before the function of breathing could be understood, Harvey would need to have discovered the circulation of blood (1628), the materiality of air would need to have been demonstrated (by Robert Boyle, who showed in the 1660s that it had weight and compressibility), oxygen would need to be discovered (by Joseph Priestly in 1774) and its properties explicated (Lavoisier, 1780 and 1790s)
And yet, there is surely, in theological, anatomical and popular tradition, a kind of metaphorical pre-understanding of the nature of breathing. Long before Robert Boyle’s measurements of the density and compressibility of air, folklore and theology alike assume the magical substantiality and power of breath. In many cultures, the action of blowing sends away the bad spirits. The winds of Pentecost naturalize the idea of holy breath. And of course the word spirit itself, substantiates the conception of the soul as contained in the breath.