During the 15th century, Florentine painters firmly believed that the motions of the mind should be apparent in the facial expressions and bodily gestures of their painted figures. This was seen to be particularly important in the case of narrative paintings.

For his painting of the Last Supper, Leonardo chose not to illustrate the moment when Judas was identified as a traitor, as was traditional. Instead he represented the preceding moment when Christ first declared the shocking words, “Verily I say unto you that one of you will betray me.” (Matthew 26:21).

Leonardo portrays the Apostles as propelled into motion by the “animal spirits” conveyed through their bodies from their sensus communis – the very seat of their soul that resides in the brain. As such, the individual movements of each figure speaks the bodily language of their mind. Leonardo has broken the convention of representing Judas alone on the other side of the table, as was the tradition in paintings of the Last Supper at that time. His stiff reaction and ugly features, which are obscured in deep shadow, make him all too apparent.

In Leoanrdo's words
One who was drinking has left his glass in its place and turned his head towards the speaker. Another wrings the fingers of his hands and turns with a frown to his companion. Another with hands spread open to show the palms shrugs his shoulders up to his ears and mouths astonished. Another speaks into his neighbour’s ear, and the listener twists his body round to him and lends him his ear while holding a knife in one hand and in the other some bread half cut through by a knife.