The justification for including this article in a volume dedicated to Sir David Ross must be that the tragic poets reflect the psychological terminology of educated Athenian society during a period which corresponds almost exactly with the life-time of Socrates and includes the first twenty years or so of Plato's life. Of course the tragic poets wrote in a poetic language strongly influenced by Homer and less strongly by lyric poetry, but they were also influenced by contemporary thinkers, doctors, sophists, and philosophers. The present study is confined to the words psyche, thymos, kardia (and its synonyms), phren/phrenes, nous.
It may be useful first to note the range of usage of these words and secondly to point out very briefly the historical development. The range of usages of these words is difficult to define; in fact such definition cannot produce boxes into which instances can be sorted but may usefully mark points on the scale of meaning between which any given instance falls. Of the five words, kardia and phrenes are names for parts of the body, ‘heart’ and ‘diaphragm’. It is perhaps rash to identify psyche and thymos with the cold/moist and hot/dry components of breath, but certainly in many passages of Homer they have some such physical meaning. Nous, however, is a verbal abstract and verbal abstracts in Greek mean not only a process but also the agent or the result of the process; as a process, it means ‘appreciating the situation’ in the military sense in which appreciate involves also making a plan; as an agent, it means ‘the appreciating mind’; as a result, it means ‘the plan or thought’ which results from the appreciation. By analogy, I suspect, with nous the other words also can be used for mental processes and results as well as for agents; thymos can already mean ‘thought’ in Homer, kardia ‘courage’ in Archilochos, and phrenes ‘intention’ in Solon. The full possible range of meaning is: (a) part of the body, (b) psychological agent, (c) psychological process, (d) result of psychological process. But these meanings fade into one another and any particular instance may be difficult to classify precisely.