What is the theme in Melanctha by Gertrude Stein?

Doubt and ambiguity first appear in "Melanctha" in the guise of a suggested gap between appearance and reality: Melanctha and her mother are both "sweet-appearing," but apparently not sweet in a simple sense. The issue of false appearances comes to its peak with Jeff's fear that Melanctha is somehow deceiving him about herself or her feelings. Ultimately, however, the simple opposition between appearance and reality gives way to some more complicated suggestions about reality—in particular, that it is difficult or even impossible to know, especially over time, what is "real." Jeff's concern that Melanctha is deliberately deceiving him becomes overshadowed by his preoccupation with his inability to know her and her feelings.