The paper advances the hypothesis that, in Thomas Reid's reading, David Hume's skepticism of the Treatise on Human Nature is not solely due to his acceptance of the ‘ideal hypothesis’ – the principle according to which ideas are the immediate objects of the mental operations –, but it has another source, namely, that doubt on the reliability of the faculties of the senses, memory, and reason. Moreover, the paper argues that the suggested distinction between two roots for Hume’s skepticism allows (...) a more exact view on Reid’s reading of Hume and solve some misinterpretations. (shrink)