The good is diffusive of itself in the way in which an end moves

"the good is said to be diffusive of its being [(lit. of itself)] in the way in which the end is said to move [(bonum dicitur diffusivum sui esse, eo modo quo finis dicitur movere)]."

     Thomas Aquinas, ST I.5.4.ad 2, trans. Ralph McInerny.  Latin from Corpus Thomisticum.