Duality
Duality was a term used to describe someone's emotional state when two personalities were in one person.

In 2364, Counselor Deanna Troi sensed a feeling of duality in Beverly Crusher and Worf after the two were occupied by the Beta Renner cloud. ()

Two years later, Troi told Captain Jean-Luc Picard about the duality she sensed in Roga Danar. ()

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Psychology