 One especially clever argument begins with the assumption that human brains think. That seems fair enough. Then Cavendish argues that the only way that human brains could think is if the elemental bodies that compose the brain were also mental and perceptive. In effect, she is asking the question: if the physical elements that make up the brain are entirely non-mental – and exhibit no trace of mentality – how could they add up to a larger brain that thinks? If the basic elements of the brain do not have any mentality at all, then they could not combine together into a larger body that thinks. That would be magic, and Cavendish is not going to appeal to magic in her explanations of things. Non-mental elements could certainly combine together to compose a larger thing that is also not mental or minded. But if elements combine together to form a brain that thinks, then those elements must have some trace of mentality or  proto-mentality.[25]  She writes,