"[3] The painting shows in a demonstrative gesture how the doubting apostle puts his finger into Christ's side wound, the latter guiding his hand.

Caravaggio, in the horizontal dimension of the canvas, "photographs" the moment of observation in a three-quarter frame in which he arranges the four figures on a neutral and dark background.

[12] The Potsdam painting belonged to Vincenzo Giustiniani before entering the Prussian royal collection, surviving the Second World War intact.

5 pal.larg.6 by the hand of Michelangelo da Caravaggio with a black frame profiled and guilloché with gold" Bellori wrote of the Potsdam painting in 1672: "St Thomas placing his finger in the wound at the Lord's side, placing his hand close to the wound and exposing his breast with a cloth, removing it from the stern".

[15] After the dispersal of the Giustiniani collection, the painting was sent to Prussia and purchased by the state in 1816, taken to Charlottenburg Palace and later to the Picture Gallery in Potsdam, where it remains today.

According to the inventory list of 19.11.1608, the first owner was the French ambassador Philippe de Béthune, Count of Selles, minister of King Henry IV.

According to historical research by Prof. Dr. Maurizio Marini and Dr. Dario Succi, Sir Denis Mahon, Prof. Mina Gregori, Dr. Federica Gasparrini, Mag.

Maria Ranacher, Dr. Michela Fasce as well as Dr. Roberta Lapucci, this painting is an autograph version by Caravaggio with the collaboration of his master student named Prospero Orsi.

Interestingly, in addition to the four figures in the final painting, the original composition contained two others that almost formed a pyramid and filled the upper part in a scenic third plane.

The result: the pentimenti discovered during the cleaning carried out on the present painting confirm that it is probably even the first version of Caravaggio's interpretation of this theme.

[22] The technical and radiographic analyses and X-ray examination have revealed pentimenti (not simple corrections) to such an extent that even the hypothesis that it is a copy seems unthinkable.

The technique of this painting, revealed in its exceptional quality, develops through overlapping layers of colour that underline a clear, explanatory project.

As far as the purely technical aspects of the execution are concerned, it was noted that the painting has a support made of a single canvas whose texture, in terms of the number of threads, appears identical to that of "Saint John the Baptist" in the Capitoline Art Gallery when compared by X-ray.

The Trieste version "The Incredulity of Saint Thomas" is published in the Maurizio Marini corpus catalogico "Caravaggio - Pictor praestantissimus" Newton & Compton - 2005 in position Q50.

[27] The painting is declared as "d'interesse artistico e storico" by the "Ministero per i Beni e le Attività Culturali Sopraintendenza Regionale del Friuli - Venezia Giulia".