* The concept of "self" and "other": Keller did not understand that she was a separate entity from her surroundings or that other people had their own thoughts and feelings.
* The concept of time: Keller did not understand the passage of time or the sequence of events.
* The concept of cause and effect: Keller did not understand that events were connected or that her actions could have consequences.
* The concept of language: Keller did not understand that words represented objects and ideas or that language could be used to communicate.