The paper advances the hypothesis that René Descartes presents a skeptical system of philosophy in Thomas Reid’s reading. There is a sort of ‘involuntary’ 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 di...