This essay deals with the early discussion of Molyneux’s question - which may hopefully cast some light on the contemporary debate – and is written from an historical point of view. I will claim that, in the eighteenth century history of Molyneux’s question, there is a leading figure: Denis Diderot; the most original and fruitful answer is given in his Lettre sur les aveugles à l’usage de ceux qui voient (1749). From the historical background of Diderot’s analysis, both the merits (...) and limitations of the negative and positive answers, along with the inadequacy of the standard classification between “empiricists” and “rationalists”, will also emerge. Diderot’s “relativistic” solution is a turning point in the whole philosophical discussion of Molyneux’s question, in that it has been confirmed by clinical reports of surgical operations of blind people, starting from Cheselden’s case. (shrink)

Euclid's definition of proportional magnitudes in the Fifth Book of the Elements gave rise to many commentaries. We examine closely two of these commentaries, one by al-Jayy and the other by Saunderson. Both al-Jayy and Saunderson attempted to defend Euclid's definition by making explicit what Euclid had only implied. We show that the two authors explain Euclid's position in a virtually identical manner.