The noun ‘affect’ derives from the Latin affectus, past participle of the verb afficere, meaning ‘to influence’. The Oxford English Dictionary (OED) compares it to the Old French affet, meaning ‘desire, passion’, and the Middle French affect meaning ‘state, disposition’. The connotations of affectus include physical, mental and emotional states and an ‘influence or impression’ (OED). Since the end of the eighteenth century, scholarly contemplations of ‘affect’ have been characterized by consideration of the relationship between mind and body, and between sensation, feeling, emotion, thought and action. For instance, in 1799, Kant distinguished between ‘affects’ and ‘passions’, commenting that ‘the former belong to feeling, so far as it, preceding reflection, renders it more difficult, or even impossible’ (OED). In 1891 J. M. Baldwin observed: ‘Affects […] are the feeling antecedents of involuntary movements; as motives, including affects, are the inner antecedents of acts of will’ (OED). Baldwin's comment draws out the idea of movement inherent in the etymology of ‘affect’: the term indicates both the impetus to movement and its effect, as one thing ‘influences’ or ‘impresses’ itself upon another.

Affect has remained a contested concept since the critical debates generated by the ‘affective turn’ (Clough 2007) that took place in the mid-1990s in the humanities and other disciplines. But studies of affect share a focus on the relationship between the body and feelings, elucidating ‘both our power to affect the world around us and our power to be affected by it’ (Hardt 2007, ix). This relationship is the subject of the two works published in 1995 which are widely agreed to have established the two main areas of enquiry about affect in the humanities: Eve Sedgwick and Adam Frank's essay, ‘Shame in the Cybernetic Fold’, which discusses Silvan Tomkins's ‘psychobiological’ Affect, Imagery, and Consciousness: The Positive Affects (1962); and Brian Massumi's ‘The Autonomy of Affect’, which draws on Gilles Deleuze's ‘Spinozist ethology of bodily capacities’ (Gregg and Seigworth 2010, 5). Theorists working in these areas frequently return to Darwin, Spinoza or Freud to explore the relationship between external, bodily and pre-cognitive energies and forces, and how they are both ‘captured’ in emotion and ‘escape’ into what Massumi (1995, 96) argues is ‘unassimilable to any particular, functionally anchored perspective’ (emphasis in the original).