Is God just in His decree and action of election and reprobation? To suggest that He may be unjust is self-contradictory, as the very nature of God is that He is good and perfectly righteous in all of His attributes.
The answer to this Theodicy question must be based upon the understanding that first, all human beings deserve hell and second, that if anyone is going to be saved it must be by mercy alone.
Have you ever asked the question, should not God show mercy to everyone? Such a question suggests that He is not right in His decrees and calls God to a human bar of justice. The word ‘should’ places such a question in the realm of sin. It is the very nature of sin to want to direct God.
Another question one may have is, Why doesn’t God show mercy to everyone? Such a question may be asked by a humble seeker of truth. Paul answers this question by pointing to Exodus 33:19 where God reveals His glory to Moses. The answer to the theodicy question then is based solely upon the glory of God. God has mercy upon whom He has mercy and passes over whom He passes over in order to demonstrate His power and glory!