 As discussed in section 3, Descartes insists that our ideas of geometrical figures and the like are ‘eternal’ and ‘immutable’ (and Malebranche takes him also to hold that they are ‘common to all intelligences’), but Malebranche wonders here how this can be possible if they are merely fleeting modes of finite minds. To identify ideas with such modes suggests that they are merely subjective representations that vary among perceivers, and whose correspondence to reality can never be established. It thus invites skepticism (or ‘Pyrrhonism,’ an ancient form of skepticism, though here the term just means radical or universal skepticism) regarding our knowledge of the essences of created things.