Discovered in 1941, autism is a fairly new concept, and scientists are still exploring what makes up a person with autism ("A History of Autism"). In the late 1800s - the period in which Billy Budd, Sailor is set - people on the high autism spectrum were not seen as "having a mental disability", but were simply seen as abnormal and crazy (Blenner, Reddy and Augustyn). People who were like Billy, who were not far on the autism spectrum, were seen as completely normal. It was also common for people diagnosed with ASD today to be seen as more innocent and childlike (Blenner, Reddy, & Augustyn). People did not suspect that there was anything abnormal about them, which explains why Billy is not diagnosed and treated equally by all his shipmates. Billy wouldn't have been diagnosed at the time, but he was high enough on the autism spectrum to have this childlike presence and innocence about him.