The world-famous mural in Milan is today commonly known as Il Cenacolo – "The Cenacle" or simply "The Last Supper." Yet this title did not come from Leonardo da Vinci himself. What the artist originally called his work has never been definitively established.

The designation Il Cenacolo only became established decades after its creation – named after the refectory of the Dominican monastery of Santa Maria delle Grazie, where the work can still be seen today.

Leonardo arranged the twelve apostles in four groups of three – each embodying one of the four fundamental temperaments according to Hippocrates. Posture, gesture, and expression follow no coincidence, but a deliberate compositional principle.

The depicted moment: Jesus announces "One of you will betray me." The apostles' immediate reactions to this shattering message reveal their temperament – directly, unfiltered, unmistakably.

The three logical forms of judgment depicted on the back wall of the hall are reflected in each of the four groups of apostles – and can be read directly from their hands: Hands aligned together represent affirmation, hands pointing away represent negation, and differing hand positions represent an indeterminate judgment.

This is most clearly illustrated in the group to the right of Jesus. The doubting Thomas raises one finger in admonishment – a clear negation: "I do not believe it." James the Elder spreads his arms in shock, embodying the indeterminate – the wavering between belief and doubt. Philip, on the other hand, places his hands together in affirmation, as if humbly asking: "Lord, is it I who will betray you?"

The flowers on the curtains are not mere decoration – they are the symbol of virtue. With this, Leonardo gives the painting a programmatic framing: The Last Supper is more than a biblical scene. It is a universal framework for solving problems – a court of conscience to which any moral question can be submitted.

Jesus stands at the center and sets the direction – through two opposing gestures that structure the entire pictorial program:

Leonardo has inscribed into this painting a complete system of thought – a tool with which any problem can be systematically examined:

The four wall hangings on the left side represent Aristotle's four causes:

The four wall hangings on the right side represent the four cardinal virtues:

Leonardo da Vinci was known for embedding hidden messages in his works. Contemporaries who expressed their beliefs too openly risked being persecuted as heretics – all the more reason to encode messages rather than speak them openly.

Anyone who looks at the painting without Christian cultural preconceptions sees not twelve men, but: a central male figure (Jesus), eleven men – and immediately beside Christ a figure with distinctly feminine features. The Church identifies this figure as the apostle John. But was that really Leonardo's intention?

Salleck considers it no coincidence that "the disciple whom Jesus loved" is depicted as a woman – and suspects this figure to be Mary Magdalene. Several striking clues support this:

The painting also shows this, but in a strikingly different way. Peter does not beckon — he grabs Mary Magdalene by the hem of her garment, pulling it so that three fingers touch Mary Magdalene's skin — the woman whom Jesus loved.

Moreover, he pulls Mary Magdalene forcefully away from Jesus and toward himself, and his hand appears to press Mary Magdalene downward, to a place where she does not belong. This may be an allusion to the fact that the Roman Catholic Church defamed Mary Magdalene as a sinner and prostitute (Pope Gregory I, year 591).

In 2009, Salleck received as a gift the book of a deceased friend, Dr. Georg Eichholz, titled "Tema Con Variazioni" (2009, Scaneg Verlag, Munich) - a work that deals intensively with the "Last Supper."

In it, Salleck discovered a previously unsolved riddle of Leonardo's: a drawing in the context of sketches for the Last Supper, the so-called "Double Emblem."

The Double Emblem shows a tree stump from which a young shoot is sprouting, as well as a falcon with a snake in its beak. Remarkably, Leonardo inscribed this drawing - unusually, not in mirror writing - with the words:

Art history has puzzled over the meaning of this drawing to this day. Salleck's interpretation of the "Last Supper" now makes a coherent explanation possible.

Leonardo had resolved not to reveal the deeper meaning of his painting. As a self-proclaimed "keeper of secrets," he lived in a dangerous time: in Leonardo's era, book burnings and iconoclasm took place in the circle of the Dominican friar Girolamo Savonarola. Openness would have brought him into serious trouble.

Nevertheless, he harbored a hope: that the true content of his work would one day be discovered - and with it the extraordinary conception and composition that makes the "Last Supper" one of the most significant paintings in the world.

The fact that Leonardo exceptionally dispensed with mirror writing in this drawing can be interpreted as a deliberate signal: the meaning was intended to be someday more easily accessible, and his genius thereby proven.