Let me try and give the LDS perspective…
To be perfect as written in Matt 5:48 is to be complete, fully formed, or finished. God is fully formed and there is no attribute or knowledge he does not posses. Thus He is perfect.
Progression then is not about reaching a greater level of perfection. Instead, God progresses in glory and honor as he exalts his children. Here is how Joseph Smith said it:
Thus God will ever be our Father and we will ever be his children. We will never reach his “level” of exaltation worlds without end.
Quote:
What did Jesus do? Why, I do the things I saw my Father do when worlds came rolling into existence. My Father worked out His kingdom with fear and trembling, and I must do the same; and when I get my kingdom, I shall present it to My Father, so that He may obtain kingdom upon kingdom, and it will exalt Him in glory. He will then take a higher exaltation, and I will take His place, and thereby become exalted myself. So that Jesus treads in the tracks of His Father, and inherits what God did before; and God is thus glorified and exalted in the salvation and exaltation of all His children. (Teachings of the Prophet Joseph Smith, 347-348)
Perfection in this context means fully realizing our nature and being. Of course God is perfectly free and hence perfectly fufills his own nature, which is goodness, truth, love, omnscience, etc., without any impediment. We will be perfect when we perfectly realize our created nature in communion with God, when we are fully what God created us to be - his adopted children. Of course we will always be less than God since we are created, finite creatures, wholly dependent on God’s grace for all the perfections we possess and for our very existence.
On the Joseph Smith quote, I can’t help but think of multi-level marketing, where everyone “below” you contributes to your cash-flow (or glory in this case).
Joseph Smith also taught:
"It is necessary we should understand the character and being of God and how He came to be so;
for I am going to tell you how God came to be God. We have imagined and supposed that God was God from all eternity. I will refute that idea, and take away the veil, so that you may see.
These are incomprehensible ideas to some, but they are simple. It is the first principle of the gospel to know for a certainty the character of God, and to know that we may converse with Him as one man converses with another, and that He was once a man like us; yea, that God himself, the Father of us all, dwelt on an earth, the same as Jesus Christ Himself did; and I will show it from the Bible."
"There never was a time when there were not spirits; for they are co-equal [co-eternal] with our Father in heaven.
**The first principles of man are self-existent with God. God himself, finding he was in the midst of spirits and glory, because he was more intelligent, saw proper to institute laws whereby the rest could have a privilege to advance like himself. **The relationship we have with God places us in a situation to advance in knowledge. He has power to institute laws to instruct the weaker intelligences, that they may be exalted with Himself, so that they might have one glory upon another, and all that knowledge, power, glory, and intelligence, which is requisite in order to save them in the world of spirits."
To me the most fundamental theological difference between Mormonism and orthodox Christianity is that in the latter God is viewed as the source of all other existence, the unique self-existing being. God has always been God. In the Mormon faith the elements and our intelligences are co-eternal with God. God is more of an organizer than a creator, who apparently progressed into his godhood and now wants to help us progress into godhood as well…
