who was the guiding spirit behind the foundation in 1603 of the Accademia dei Lincei. His multi-volume De Refractione Optices (1593) was particularly concerned with optical matters, the second volume being devoted entirely to the incidence of light on water-filled and glass spheres. The circle of Della Porta was significant for Caravaggio later on in Naples, where the commission for the Seven Acts of Mercy seems to have emanated from Giovanni Battista Manso, Marchese di Villa, whose friend, the alchemist Colantonio Stigliola, was a member of the Accademia dei Lincei. The appearance of second originals is a feature of a new understanding of Caravaggio's work, and indeed Vincenzo Giustiniani, whose experience was closely related to the artist's career, describes in his Discorso sulla pittura the painter's development as beginning with copying others’ work – 'Proceeding further, he can also copy his own work, so that the replica may be as good, and even sometimes better, than the first'. The procedure for making a second version was, however, substantially different from the sometimes very arduous task of building a group from many separate observations of reality, of figures and objects; it is natural that the 'second original' is sometimes more fluent than the first. The anatomical anomalies in the Wildenstein and Badminton House paintings, like the slightly out of line eyes, or the hesitations in the profile of the hand, are resolved in the Hermitage picture. By contrast, the Hermitage version is more cursory in the drapery, less insistent in the detail, and it does not have the magnificent reflections in the carafe, which were specific to the alchemical context of the original. This is also the reason for the jealousy with which the group of pictures was regarded by Caravaggio's patron Del Monte, and for the misunderstanding that the pursuit of natural philosophy incurred in the Rome of his day. The Wildenstein version was sold by Del Monte's heirs to Cardinal Antonio Barberini in 1628, when it was described as "Un giovane che sona di clevo" (without an attribution) and included with St Catherine and the Cardsharps (named specifically as by Caravaggio) and various other paintings. The painting is illuminated by a soft chiaroscuro inspired by the Brescia masters of the 16th century and characteristic of the early phase of Caravaggio's development. The catalogue to the 1990 exhibition held to mark the identification of the Wildenstein Lute Player – which