Final answer:
Dr. P., as discussed by Oliver Sacks, suffered from visual agnosia, a disorder characterized by the inability to recognize objects visually.
Step-by-step explanation:
In the account by Oliver Sacks, Dr. P. suffered from visual agnosia, a neurological condition that affects the ability to recognize and identify objects or faces, despite having good vision. To provide examples and relevant information, a famous illustration of this condition can be found in Sacks' book 'The Man Who Mistook His Wife for a Hat,' where Dr. P.'s case is discussed. Another concept mentioned is dissociative identity disorder, explored in an article by Piper & Merskey (2004), which critiques the excesses of the concept. Lastly, the question alludes to grave misunderstandings in psychological literature, such as the notion of homosexuality as a sickness, highlighting the evolution of medical and psychological understanding over time.