"The Decameron" by Giovanni Boccaccio is a work which stands between the Middle Ages and Modernity. There are theories which postulate that concepts of identity and individuality, which arose with the dawn of Modernity, have an influence on mental illness. We chose a hermeneutic approach towards "The Decameron" to analyse the depiction of a changing society, of love, mental suffering and the role of therapeutic interventions. We conclude that Boccaccio showed an interest in intrapsychic mechanisms, an idea pertaining to Modernity, and discuss this idea in light of today's psychiatry and Karl Jaspers' concept of "genetic understanding".