Ribera painted a series of twelve philosophers for Don Fernando Afàn de Ribera, 3rd Duke of Alcalá and Viceroy of Naples between 1629 and 1631. It is difficult to retrace the paintings that originally formed part of this original set, since Ribera's workshop was immediately summoned to produce similar series for other patrons, some of which were painted by Ribera himself and others executed by his studio assistants. The originals are today scattered between public and private collections; the prime version of Thales has been identified as the picture formerly with Galería Caylus, Madrid, now in a Parisian private collection (see N. Spinosa, Ribera. La obra completa, Madrid, 2008, p. 369, no. A109).
While it is relatively easy to recognise straightforward copies, it becomes much more difficult to distinguish autograph versions from good workshop replicas. On the basis of photographs, Professor Spinosa, to whom we are grateful, considers that the quality of this painting indicates that it may be an autograph version.