 In the Treatise Condillac focused just on our pre-linguistic cognitive abilities, which he came to think he might have underestimated when he wrote the Essay. He retracted his earlier claim that perception is a transparent process and accepted both that it involves unconscious inference from what is given in sensation and that sensation itself may contain more than it is at first perceived to contain. He also retracted his earlier claim that depth is immediately perceived by vision. To support these revised opinions, he proposed a famous thought experiment. He asked his readers to consider an originally inanimate and insentient human being (Condillac spoke of a being that is just a “statue” of a human being) and to consider what this being could come to know were it to acquire each of the senses in isolation from the others, or each in combination with just one or two others. In proposing this question Condillac was asking a more radical version of the question Molyneux had posed to Locke: would a person born blind and made to see perceive spatial features well enough upon first sight to be able to identify cubes and spheres without touching them? Condillac was asking what a person endowed with just a sense of smell would think upon acquiring the power of hearing, or what a person endowed with vision would know if unaffected by hunger, incapable of motion, and unaware of any tactile sensation. His answer to these questions sought not just to explain how this person would acquire ideas of space and of external objects, but to prove that nothing more would be needed for it to acquire all the knowledge and all of the abilities that we have other than just to experience a sufficiently rich array of sensations.