Brain-scan-based diagnostic machines could take account of the social factors only insofar as they are factors that leave discernable traces in the brain. If social factors leave no such traces, then methods of diagnosis that are based only on brain scans would inevitably be blind to them. A brain-scanning enthusiast might think that this limitation of brain scanning could not possibly be of any clinical significance. Anything that influences a brain’s functioning must make some difference to that brain. It follows from this that those social factors that make no difference in the brain could not possibly be playing any immediate role in the explanation of that brain’s functioning. There would be significant difficulties for any system that attempted to make psychiatric diagnoses only on the basis of data from brain scans, however much of that data was available.