Roget's Thesaurus by Peter Mark Roget

2. Causes of Volition

#615. Motive.—N. motive, springs of action, wellsprings of action. reason, ground, call, principle; by end, by purpose; mainspring, primum mobile[Lat], keystone; the why and the wherefore; pro and con, reason why; secret motive, arriere pensee[Fr]; intention &c.