(n.) Something that promotes a reaction or change; as, a catalyst to improvement; a catalyst to oxidation\.

agent agent provocateur agitator agitprop alterant alterative alterer author begetter beginner catalysis catalytic agent causer creator decay demagogue dialysis dissociation effector engenderer exciter father ferment firebrand fission fomenter generator goad hydrolysis hydrolyst impetus impulse incendiary incentive incitation incitement inciter inflamer innovationist innovator inspirer instigator introducer leaven maker mischief-maker modificator modifier mother motivation mover originator parent photolysis precursor prime mover primum mobile producer provocateur provoker rabble-rouser ringleader rouser seditionary seditionist sire splitting spur stimulant thermolysis transformer transmogrifier troublemaker urger yeast