This chapter focuses on the domain of the vegetative soul that represents some of the simplest activities that distinguish the organic from the inorganic. It examines the central vegetative system consisting of the liver, the veins and their supporting organs, as well as the vegetative capacities present in all the tissues that are subservient to this system. The chapter not only discusses the relationship between the central parts and capacities in all of the body, but also examines the ways in which these capacities manifest themselves, arguing they represent Galen’s attempts to grapple with the notion of basic vitality. On some occasions, Galen also calls them ‘demiurgic’, implying a creative capacity. A discussion of how he engages with the pre-existing philosophical tradition and the notion of a biological demiurge helps to delineate the scope of these capacities.

The first and most important step into the Peripatetic study of living beings is the observation that life takes many forms. In the sublunary world, it takes the form of plant and animal life (with human life as a special kind of animal life). When Aristotle and Theophrastus speak of animals and plants, they never assume that they are a single form of life. This is confirmed by what we read at the outset of the Meteorology, where Aristotle outlines an ambitious research program that ends with separate yet coordinated studies of “animals and plants.” Whether there is unity, and how much unity there is, in these two studies remains an open question at the outset of the Meteorology. But when we look at the two corpora of writings that Aristotle and Theophrastus have left on the topic of animals and plants, we see that the unity they are able secure is limited. Last but not least, this chapter shows that the study of the nutritive soul advanced in Aristotle’s De anima cannot secure unity within the study of animals and plants.