 Health has received less philosophical attention than disease, and this essay will correspondingly have less to say about it. The conceptual terrain in the case of health is a little more complex than that of disease; one way of thinking about health says that it is just the absence of disease, so if disease is biological malfunction or abnormality, it follows that a healthy person is someone whose biological systems are all in order. But another way of looking at health insists that it is not just the absence of disease but the presence of something more; a positive state. The constitution of the World Health Organization (WHO) defines health “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” (WHO 1948). According to views like this, we should think in terms not of health and disease alone, but in terms of health, disease and normality. This essay will look at theories of health after first discussing disease. The focus throughout is on individuals, although some theorists (e.g. Inkpen 2019) have argued for a seeing humans and their associated microbiomes as part of an ecosystem that can be evaluated, like other ecosystems, as healthy or not. 