know whether one is Arthur or Martha

Verb

 * 1)  To be in a clear state of mind.
 * 2) * 2012, Marie-Therese Gould (Stein), Dirt to Scratch and Eggs to Lay: A Journey From Mitchell to Ma’s, Xlibris Corporation (ISBN 9781477155165), page 241:
 * The poor little darling had so many mothers; she didn't know whether she was Arthur or Martha!
 * 1) * 2012, Marie-Therese Gould (Stein), Dirt to Scratch and Eggs to Lay: A Journey From Mitchell to Ma’s, Xlibris Corporation (ISBN 9781477155165), page 241:
 * The poor little darling had so many mothers; she didn't know whether she was Arthur or Martha!

Usage notes

 * Almost always used in the negative.