Is the glass half empty or half full

"Is the glass half empty or half full?" is a common expression, a proverbial phrase, generally used rhetorically to indicate that a particular situation could be a cause for optimism (half full) or pessimism (half empty), or as a general litmus test to simply determine an individual's worldview. The purpose of the question is to demonstrate that the situation may be seen in different ways depending on one's point of view and that there may be opportunity in the situation as well as trouble.

This idiom is used to explain how people perceive events and objects. Perception is unique to every individual and is simply one's interpretation of reality. The phrase "Is the glass half empty or half full" can be understood also as a philosophical question.

Another perspective comes from psychology, where research has shown that a speaker's choice of frame can reflect their knowledge of the environment, and that listeners can be sensitive to this information.