Aquinas can tell us, but can't think for us

THOMAS Aquinas predicts where certain of our thoughts come from--God.
    We hope what goes on inside us tallies with his rulings.
   Of course in his day, if you didn't agree with his pronouncements, you kept it to yourself.
    Aquinas says the eye sees an object because it is illuminated by the sun. The 'eye' of the intellect sees truth because it is illuminated by God.
     How do I know it is God illuminating my thoughts?
     I hope it is, but I doubt he is responsible for all my thoughts...