motive

(noun): An idea or communication that makes one want to act, especially from spiritual sources; a divine prompting.
(noun): An incentive to act in a particular way; a reason or emotion that makes one want to do something; anything that prompts a choice of action.
(noun): A limb or other bodily organ that can move.
(noun): Something which causes someone to want to commit a crime; a reason for criminal behaviour.
(noun): A motif.
(noun): A motif; a theme or subject, especially one that is central to the work or often repeated.
(verb): To prompt or incite by a motive or motives; to move.
(adjective): Causing motion; having power to move, or tending to move
(adjective): Relating to motion and/or to its cause

No-one could understand why she had hidden the shovel; her motives were obscure at best.
If you listen carefully, you can hear the flutes mimicking the cello motive.
a motive argument