animal spirits

noun[plural only]3

1. •
   Liveliness, vivacity, a happy tendency to action.
2. •
   After Keynes (citation 1936, above), the emotional and intuitive factors that drive business decisions whether to make investment gambles.

   • The existence of animal spirits does not imply that "irrational psychology" is the controlling factor in business and economics. — 2005
3. •
   (historical) The theorized ‘spirits’ or physiological principles which allowed for sensation and voluntary movement.

   • His Brains will be found situated at the Head of the Os Pubis: His Animal Spirits acting more vigorously in that Part, than in the Upper Region. — 1723