decartes
Descartes arrives at the conclusion in his second Meditation that he thinks, therefore he is. It is very possible for him to come to this conclusion with out his senses. In the matter of his thinking, he arrives at the idea that what if he does not think. But if he does not think he could not doubt his existence or the existence of other things. If he does not think, he could not be doubting his existence and the existence of other things. Even if there was an ‘evil demon/deceiver” to be faking his existence, he would not be able to come to that conclusion without existing and thinking.