Neurological and psychiatric disorders have long been regarded as fundamentally different, depending on whether they appear to affect the brain or the mind. In reality, the brain and the mind are inseparable. Both types of disorder can affect every aspect of brain function: from perception, action, memory and emotion to empathy, social interaction, attention and consciousness. It is easy to view brain disorders as simply tragic or frightening. However, studying where these functions go wrong provides a window on the workings of the healthy brain, and makes it more likely that scientists and clinicians will be able to develop effective treatments or preventative strategies. As individuals, and as a society, we are also able to better empathise with people with disorders of the mind. Building on his pioneering research, Eric R. Kandel illustrates how breakthrough studies of brain disruptions can deepen our understanding of thought, feeling, behaviour, memory and creativity, and perhaps in the future will transform medical care and lead to the development of a unified theory of mind.