motive (n.) 3
instrument, agent, moving organ
AW IV.iv.20 [Helena to Widow, of Diana] heaven ... hath fated her to be my motive / And helper to a husband
R2 I.i.193 [Bolingbroke to King Richard] my teeth shall tear / The slavish motive of recanting fear [i.e. the tongue]
TC IV.v.57 [Ulysses to Nestor, of Cressida] her wanton spirits look out / At every joint and motive of her body