motivative(s = adj.all) motivating, motive - impelling to action; "it may well be that ethical language has primarily a motivative function"; "motive pleas"; "motivating arguments"
Derived form verb motivate₁

   causing motion or impelling to action; providing a motive{2}; as, motivating arguments. [WordNet 1.5]
"It may well be that ethical language has primarily a motivative function"