 How, then, is it possible to doubt such matters? According to one interpretation, the answer is that we cannot doubt them directly, however, we can doubt them in an indirect manner. That is, rather than directing the doubt at particular such propositions, as that I exist, or that 2+3=5, the doubt is instead directed at the cognitive faculties by which we apprehend such propositions. By way of analogy, consider that if a calculator were defective, it would cast doubt on any calculations it generated. Likewise, if my own mind were in some sense defective, this would cast doubt on any matters I apprehended – no matter how evident those matters might seem. By directing the doubt at the veracity of my own cognitive faculties, I do thereby indirectly doubt the particular propositions apprehended by means of those faculties.