The paper advances the hypothesis that René Descartes presents a skeptical system of philosophy in Thomas Reid’s reading. There is a sort of ‘involun-tary’ or ‘accidental’ skepticism that results from the adoption by Descartes of both a skeptical method and a skeptical principle. The first section shows to what extent the Cartesian method of doubt – which focuses on the reliability of the faculties of the mind - is a skeptical demand that cannot be satisfied. The second section shows how (...) the principle of the Cartesian system – which establishes that ideas are the immediate objects of the operations of the mind – is not only skeptic but leads exactly and naturally to the most radical form of skepticism, namely, solipsism. The third section discusses the Cartesian sources of the doubt on the existence of external world according to Reid. (shrink)