The ultimate standard of morality is the will of God.
That is right which conforms to and promotes the will and purpose of God in creation.
So far as men are concerned, the will and purpose of God is the manifestation of His own glory.
That glory is manifested in the creation and perfect development of free rational human beings.
That development is attained by the whole-hearted obedience of men to the will of God.
So, then, rightness of conduct consists in obedience to the law of God, or subjection to His will and purpose. What this will is, is revealed to the reason, so that reason provides the immediate objective standard of morality. For reason, whether by intuition, discursive argument or revelation, perceives what is and what is not consonant with God's will.
The human reason, arguing correctly and perceiving truly, grasps the divine will, and the conclusions thus arrived at are the immediate objective standard of morality.