The Powers of Aristotle’s Soul by Thomas Kjeller Johansen (review)

In The Powers of Aristotle’s Soul, Thomas Kjeller Johansen offers a fresh treatment of Aristotle’s De Anima, showing that Aristotle can successfully explain the cause of life and activities of living things by appealing to a minimal number of definitionally independent capacities, in much the way that a faculty psychologist would. Johansen situates Aristotle’s account of the soul within the framework of his natural philosophy, arguing that the definitional independence of the soul’s capacities does not conflict with the internal unity of the soul. In doing so, he offers explanations of the further abilities and capacities of the soul, including phantasia and locomotion.

In the first eight chapters of the book, Johansen places Aristotle’s account of the soul within the framework of his natural philosophy, and shows how the soul may be considered as the formal, final, and efficient cause of a living thing. In chapters 2–4, Johansen offers general theoretical considerations that will be useful for explaining Aristotle’s account of the soul and its powers, and in chapters 5–8, he offers an innovative interpretation of the soul as the efficient and formal cause of a living thing. In the later chapters of the book, Johansen argues that the three parts of the soul—the nutritive, perceptual, and intellectual capacities—are sufficient for an account of the soul; other activities and abilities of living things are subsumed under one of these primary faculties. In chapters 13 and 14, Johansen suggests that other works, including De Sensu and the Parva Naturalia, can offer specific details about the capacities of animals because the definitional constraints of De Anima have been lifted.

Johansen takes on an extraordinarily difficult issue for Aristotle’s account of living things: he examines the relationship between (1) the soul, taken as a single entity, which acts as the efficient, formal, and final cause of a living thing; (2) the parts or faculties of the soul; and (3) the specific variations and functions of the primary parts of the soul found among various living things. In explaining the relationship between (2) and (3), Johansen’s interpretation is immensely plausible: the specific variations found among different living things must be explained by reference to a primary capacity, and, likewise, the definitional constraints of De Anima indicate that a thorough investigation of these further variations is a topic proper to a different treatise.

On the relationship between (1) and (2), Johansen’s interpretation is not as successful. On Johansen’s reading of De Anima, the parts of the soul are definitionally independent from one another, where definitional independence is understood symmetrically. Despite the definitional independence of the soul’s parts, the soul is unified because the parts are present in the whole in the way that matter is present in form. Johansen suggests that the relationship of the parts to the whole is one in which the parts are definitionally prior to the whole; if the whole were definitionally prior, then capacities for nutrition and perception would depend upon the kind of soul to which they belong.

Nonetheless, it is unclear how one might explain the unity of the whole soul without appealing to the priority of the whole over its parts: if not the whole soul, there is no clear source of unity for the particular, individual powers of the soul. Aristotle offers a hint in Metaphysics Z.10, but, without further elaboration, it remains uncertain that the soul is a unified being and not a mere aggregate of parts with independent powers and functions. Indeed, this is not a worry for Johansen’s interpretation so much as it is a general worry for Aristotle’s account of the soul; although Johansen makes good sense of the tension between modularity and holism, particularly in the final chapter of the book, he is not entirely able to save Aristotle from a pressing dilemma: either the soul is an aggregate of...