‘From theory to practice’ explains that autistic disorders are far too heterogeneous and too complex for a single satisfying account. It is frustrating that there is no answer yet to what causes autism. There are many different risk factors, genetic and environmental. The effect of these causes is on the mind as much as it is on the brain. Autism is a neurodevelopmental disorder, which appears to be due to a disorganization of brain development. The different areas of knowledge about autism are summed up under the headings biology, mind, and behaviour, and the ways different aspects of the condition might fit together are explored.