Every ought is ground in an is

Every ought is grounded in an is; the good is what corresponds to reality. If anyone wants to know and do the good, he must direct his gaze to the objective world of being; not to his own mind, not to his own conscience, not to values, nor to ideals or paradigms he has himself drawn up. He must look away from his own act and toward reality.
— Josef Pieper, No One Could Have Known

And if is is I Am Who Am, why consult myself?