In De pictura Leon Battista Alberti states that the power of giving visible presence to people who are absent makes the painter like a god, but that his true achievement is inventing and composing a ‘story’ (historia). Thus De pictura not only deals with how, in his picture, the painter reproduces what he sees, but also considers how the picture involves the observer emotionally in the events that are portrayed, and how what is painted persuades by acting on the motions of the soul.
Alberti writes: «the ‘historia’ will move the soul when the persons depicted in it clearly display the motions of their own souls» («moverà l’istoria l’animo quando gli uomini ivi dipinti molto porgeranno suo proprio movimento d’animo»). In other words, the person observing the painting feels the emotions, and understands the story that is being told, by participating empathetically in what Aristotle called the ‘affections’ shown by the protagonists, if these are represented by the right gestures and expressions. The means to empathetic participation known to the humanists as acting in rhetorical persuasion, in the theatre and in ancient paintings are recognised by Alberti as valid in his own time and at work in modern painting, and they thus form an early example of a theory of the affections and motions of the soul.