rational motive (noun)

1. In the world of fashion, the rational motive behind wearing high heels is to enhance posture and lengthen the legs.

2. In science fiction, the protagonist's rational motive for building a time machine was to prevent a catastrophic event from occurring.

3. In the horror genre, the rational motive for the character investigating the haunted house was to uncover the truth and rid the place of evil.

4. In comics, the superhero's rational motive for fighting crime is to protect the innocent and ensure justice prevails.