Through the eighteenth-century uses of the image of the bâton de

l’expérience, this contribution aims to investigate the specific features of certain libertine practices of Enlightenment thought. The image of the bâton de

l’expérience is given ambivalent meanings by Émilie du Châtelet: referring to
the Cartesian passages where it appears for the first time, her Institutions de
physique make it a metaphor of the ambivalence of experience, also connecting
it to the debate on the problem of Molyneux that, following the operation of
removal of cataracts from a man born blind performed by Cheselden in 1728,

had acquired new vigour. Against the background of du Châtelet’s cultural op-
eration, we will focus on two fundamental stages of the eighteenth-century uses

of this image. First, we will investigate the specific relations established between
L’homme machine and L’homme plus que machine, showing how the image of
the bâton de l’expérience is configured as a sort of key becomes functional to
the production of a libertine thought through the parallel reading – between
the lines – of the two texts. Then, we will show how Denis Diderot recovers this
image in the context of the discussion on Molyneux’s problem and using it as a

privileged perspective to discuss the statute of experience and its fictional substi-
tution. Through the image of the bâton de l’expérience, then, the permanence of

seventeenth-century libertine practices in the philosophy of the Enlightenment
will become clear: this metaphor thus redefines the conflicting and productive
relationship between light and shade in the Enlightenment.