We believe in Absolute truths that exist. Right is right and wrong is wrong. These concepts are not superficial and a creation in our minds.
These absolute truths do not limit God but rather make God complete since without these truths there would be oppression and God is not oppressive. Without them God would be ignorant and that is not the case with God. God would be unjust if He expects us to live with certain truths and He does not implement them.
The Quran says كتب على نفسه الرحمة
God made mercy incumbent upon Himself, since without it God wouldn’t be complete.