The process that gives rise to the central nervous system. This process pertains to the initial formation of a structure from unspecified parts. The central nervous system is the core nervous system that serves an integrating and coordinating function. In vertebrates it consists of the brain, spinal cord and spinal nerves. In those invertebrates with a central nervous system it typically consists of a brain, cerebral ganglia and a nerve cord. [ http://purl.obolibrary.org/obo/go/references/0000021 https://www.worldcat.org/search?q=bn%3A0582227089 GOC:jid GOC:cls GOC:dph GOC:dgh ]