In this text, of which we have translated a large excerpt, Olivi defends his own version of the identity theory of the soul and its powers. On this version, the soul is a bundle of powers (plus spiritual matter), and so is identical to the entire collection of its powers (plus spiritual matter). To defend this view, Olivi first considers and rejects another version of the identity theory, on which the soul is a single power capable of eliciting all of the different vital acts associated with a living being. His main argument against this position is that diverse forms of production or of activity require powers that are themselves diverse by nature or essence. Olivi then attacks the distinction theory developed, for instance, by Aquinas, arguing that, among other things, this theory conflicts with our conception of ourselves as essentially free and rational agents. Next, Olivi criticizes Bonaventure’s distinction theory, arguing that it is impossible for the soul’s powers to be substances and yet dependent on the soul itself. Finally, Olivi puts forward his own preferred bundle theory of the soul and its powers.

In this text, Ockham deals with whether memory, intellect, and will are really distinct powers. He answers in the negative. After presenting first Aquinas’, then Henry of Ghent’s, and finally John Duns Scotus’ views in some detail, along with replies, Ockham presents his own uncompromising identity theory of the powers of the soul. Based on the principle of parsimony, he argues that the rational soul is identical to the intellect and the will. By transitivity, this entails that the intellect is identical to the will so that the rational soul is a single power to engage in acts of thinking and and willing. Fleshing out his view, Ockham also gives a sort of rule for knowing when distinct cognitive and appetitive powers must be posited, and when not. According to this rule, if everything outside of a cognizer or desirer remains the same, and the cognizer or desirer is able to have an act of one power, while being unable to have the act of another power, then those powers must be distinct. For example, some people may be unable to see while being able to hear and other people may be unable to hear while being able to see. It follows that sight and hearing must be distinct powers.

In this text, Durand rejects a common assumption undergirding much of the Latin medieval debate about the relation between the soul and its powers. According to this assumption, which we can call the uniformity assumption, all powers of the soul that bring forth vital operations, such as the intellect and sight, bear the same relation to the soul. Identity theorists maintained that all of these powers are identical to the soul, while distinction theorists held that all of these powers are distinct from the soul. Against this consensus, Durand argues that some powers of the soul are identical to the soul, while others are distinct from it. More precisely, he advocates an identity theory with respect to the vegetative powers but a distinction theory with regard to the sensory and rational powers. He motivates his identity view regarding the vegetative powers with the argument that these powers have substances as their effects and the premise that causes must be like their effects. To motivate his distinction theory regarding the sensory and rational powers, Durand does not draw on Aquinas’ Category Argument, which he thinks is unsound.

This chapter discusses the contextualization of human traits in social roles. It begins by exploring how personality traits relate to social roles, then it extrapolates those findings related to virtues and discusses theory and research on social roles and virtue traits. The discussion of the social role contextualization is based on identity theory, which explains that social roles are repetitive patterns of action that are included in social structures and result in role identity formation in the individual. The chapter reiterates that up-to-date trait conceptualizations do not view them as simplistic behavioral tendencies that manifest in any social role. Instead, traits are currently understood as influenced by social role expectations. Practical wisdom plays a large part in the expression of virtues through social roles. Practical wisdom adds an element to virtue expression and social roles that is absent in personality research because some individuals see more opportunities for virtue trait expression within a role than others. It then clarifies this theoretical discussion with examples of common role and virtue enactments from the parenting, teaching, and healing roles. It concludes by discussing how a virtue perspective adds important elements (agency, aspiration, and practical wisdom) to the contextualization of traits.

The Introduction discusses paideia (culture of Greek intellectuals) and its relevance for fourth-century clergy by providing a background to the Cappadocian Fathers. The chapter defines the meaning of "classical masculinity" for this study and places its treatment of gender into the broader scholarship on late antiquity and Christianity. The chapter outlines key concepts such as aretē (manly virtue), agathos (superior person), and asceticism (self-denial), and introduces agōn (contest or struggle) as the concept around which the book is organized. It also directs the reader to consider the Second Sophistic as the antecedent to the fourth-century culture of epistolary exhibitions. The chapter explains the differences in the Cappadocians’ use of genre and the distinguishing features of epistolography and hagiographic biography. And the Introduction explores identity theory and its usefulness for investigating gender and Christianity.

The conception of this handbook goes way back, taking us more than five years until completion. It all began with an early plan to organize a symposium for the 31st International Congress of Psychology (ICP) for July 2016 in Yokohama, Japan. The intention was to bring together a group of international identity researchers, from within psychology and from neighboring disciplines, to see whether there were any new developments in identity theory and empirical research, and whether they had a common center or were drifting pieces moving in all kinds of directions (cf., for example, Nochi, 2016, or Watzlawik, 2016). This was the original idea. So, in the summer of 2015 we started contacting researchers we knew (and whom we did not know up to that moment), asking whether they would be interested in joining us for the symposium. Preparing the symposium was as stimulating as the actual gathering that took place on the afternoon of July 28 one year later under the header Identity and Identity Research in Psychology and Neighboring Disciplines. Janka Romero, the Commissioning Editor for Psychology at Cambridge University Press, had contacted us beforehand with the offer to talk about the potential to turn this into a book project, and we, the symposium participants, started following up the same night over dinner – not knowing that this would keep us busy for the next five years. We went through the usual editorial routines: developing a proposal, revising the proposal, and contacting old and new colleagues in the field, up to the point of delivering the full set of manuscripts in January 2021.