 A final observation. It is often unnoticed that the conclusion of Descartes’ argument for the existence of an external material world leaves significant scepticism in place. Granting the success of the argument, my sensations are caused by an external material world. But for all the argument shows – for all the broader argument of the Meditations shows, up to this point – my mind might be joined to a brain in a vat, rather than a full human body. This isn’t an oversight on Descartes’ part. It’s all he thinks the argument can prove. For even at this late stage of the project, the meditator has not yet established himself to be awake – a line of inquiry to which we now turn.