 No medical procedure to do with consciousness has received as much philosophical attention in recent times as commissurotomies, more commonly known as brain bisection operations. Nagel (1971) was perhaps the first philosopher to write on them; his paper continues to be influential. Since then, Puccetti (1973, 1981), Marks (1981), Hirsch (1991), Lockwood (1989), Hurley (1998), Bayne (2008, 2010), Schechter (2010) and many, many other philosophers have written on these operations. Indeed, the strange results of these operations in certain controlled conditions was one of the things that brought the unity of consciousness back onto the cognitive research agenda. 