The senses deceive me sometimes; they can thus deceive me all the time, and I will therefore submit to doubt all knowledge whose origin is in sensation): All that up to the present time I have accepted as most true and certain I have learned either from the senses or through the senses; but it is sometimes proved to me that these senses are deceptive, and it is wiser not to trust entirely to any thing by which we have once been deceived.