Why didn't God just create us perfect in heaven?

If God exists, then God is obviously the ultimate source behind God's own decisions. Similarly, most Christian philosophers will say you are the ultimate source behind your own decisions, and your resemblance to God in this aspect and others is what makes you an incredibly valuable thing. In fact, if the story of Jesus as told below is true, God has taken very costly steps to essentially adopt you as a genuine resembler of God, so that when God finally destroys evil, you can nevertheless dwell with Him in relationship for eternity while retaining that value. God's plan allows you to do two things:

• First: Be cleansed of any sin that would prevent you from dwelling with God in the first place,
• Second: Choose for God to transform you into something that will never sin again so you can stay there.

Let me explain the story and why God's simply creating you in heaven without the ability to sin is something God literally can't do. In short, what would be created in that case wouldn't be “you”, and wouldn't have the child-like value to God that you have.

God is all-good

The case for the existence of God, as traditionally defined, is strong. If this God exists, we are likely created BY God, FOR God, to recognize him AS God: the “greatest conceivable being”. For this and other reasons, God is thought to be a “necessary being”, meaning that just as {9 + 9 = 18} cannot fail to be true, regardless of what theoretical changes you can make to reality, so too {God exists} cannot fail to be true. There are similar arguments concluding that, if God exists, then God is necessarily the foundation and locus of value in the world, and so presumably cannot deviate from being perfectly honest, just, loving, and so forth. God is the source that coherently knits these otherwise inexplicably diverse properties together as “good.”

So God wants (#1) a perfect world and (#2) real free children

Given this maximally valuable foundation to reality, we'd soonest expect God to create the best kind of world-situation possible. A merely perfect yet empty world is not enough. The best kind of world-situation is a perfect world populated by the most valuable things that can exist. Given God is the locus of value, it would be populated by God-resembling things. To be God-resembling, these maximally valuable creations would therefore need to echo God in being dignified with rationality, knowledge, power, free will, and presumably this ability to source our own moral choices to be honest, just, loving, and so forth. Notice this “best kind of situation” is synonymous with heaven, and so we can see why heaven might be thought highly likely to exist right now if God exists.

But #1 and #2 can't co-exist in one step

So then here comes our question: if a forever sin-free heaven is possible, why not create that heavenly situation right now? In short, God resembling agents who are sources of their own moral life and yet never sin on their own ostensibly can't be created or produced in one step. Look at our world. It turns out that given enough opportunities, sinning is just what we freely choose to do over time. God will naturally always act lovingly etc. in accordance with His nature, but what would stop us from choosing at times in heaven to act differently? Obviously then, if God created us in a heaven-like world as we are, without God’s intervention, we did or would corrupt it not long after!

Step 1: Get free submitters, Step 2: destroy evil (all else)

This is why God's obtaining real children who are compatible with heaven, by logical necessity, requires two steps:
Step 1: Create moral agents in an arena where they can be the choosing source of this defining moral choice: whether or not to permanently morally submit to God and His ability to prevent them from sinning. (Think here of freely inviting a perfect co-driving wreck-preventer into your car. You drive, but you would ultimately like him to always reach his hand over onto the wheel right when needed to prevent you from turning the car wrongly. So he perfects your driving.)¹
Step 2: Then destroy or partition off every wreck and every driver that does not choose to fully submit to God’s wreck-preventing influence; i.e. all evil and everything still capable of producing evil: As Jesus put it, the time is coming...

• Matthew 3:12 -- “[God] will gather His wheat [those who cooperate] into the barn, but He will burn up the chaff [all potential heaven-destroyers who never submitted their steering wheel] with unquenchable fire.”

So why didn’t God just create us in heaven without the ability to sin, by forcing his way into our car from the get-go as a coercive co-driver? The answer is: because then God would have been the ultimate source of who we are morally, and in addition to arguably erasing us as real persons, that would absolutely break our resemblance to God. Only if we invite God as co-driver is our moral life in heaven—God's steering corrections included—grounded in our decision. Only then does our heavenly life flow in source-like fashion from ourselves. It's like us freely throwing away our cigarettes, of our own volition, so we can't use them henceforward. You can ask to throw away sin! So aside from these two steps, there is literally no other way to obtain the “best kind of situation” of a perfect world with true God-resemblers like us.

But God can't ignore past sin: it must be punished

But what about the evil wrecks that we have already caused? All of us are guilty of bad driving.¹ A righteous judge like God can't pretend you didn't steal from or bully that other person, right? That wouldn't take your crime or its cost seriously. The more pure and holy God is, the more lying, stealing, raping, murdering etc. will shock, repulse, and righteously enrage God. Recall then that God is perfectly holy, so we all ought to be terrified at whatever punishment we deserve before going to heaven. At the time of judgment, our sin will be decisively punished² by this sovereign, holy Being.

So God became human (Jesus) to pay our penalty for us

God seems to have set up a system in nature so that as we break God's commands, we are naturally marked with more and more “sin”—a sort of spiritual dirt or debt that targets us for a corresponding amount of righteous punishment when God's judgment comes.
As it happens, however, God is not only just, but also loving. And so in c. AD 30 Israel, none other than God incarnate (Jesus Christ)-—visiting Earth as man—-took on a special substitute role for those described above, who give themselves to God. What role is that? God lived in flesh without sinning even once, and His ministry of love and miracles culminated in His being nailed to a wooden cross, where He also took on all your debt and received the corresponding Divine punishment you would have taken for it. In so doing,

◦ “…He Himself bore our sins in His body on the cross” (1 Pet. 2:24)
◦ “…He has taken it out of the way, having nailed it to the cross.” (Col. 2:14)⁴

It was a spiritual agony.³ So, borrowing the words of Isaiah 1:18,

◦ “‘Come now, and let us reason together,’ Says the LORD, ‘Though your sins are as scarlet, They will be as white as snow’”

This swap—this salvation from due judgment—is a free gift available to anyone who asks God and chooses to align their will to His. What's more, on these children who choose to submit to the Good, God forever lavishes His mercy and grace and blessing. Nothing is withheld from His beloved. In summary, for those of us who submit to God's transformation, we are gifted with two things:
a) God's “Holy Spirit.” With God's personal presence and influence in us, we can start now enacting our decision to submit to God as moral co-driver, and taste every day what it is that we're asking to experience an eternity of. This is relationship with God. He won't always stop you from wrecking, but you'll notice new aid in moral living.
b) A clean slate. Despite all of our previous sin and due punishment, we are gifted with a now debt-free record. Jesus pays the penalty in full for us..
In heaven, God will stop every wreck you might cause, so with your slate clean, this is everything you need to be compatible with the perfect world God is bringing!

How to become a child of God

• Understand that you are guilty, and hate your sin (repentance).
• Understand that God, in love, has mercifully provided a way to reconcile you to Him. And in fact, Jesus's paying your sins and co-driving is your only way into heaven.
• Understand that Jesus is Divine (a part of God), and His righteousness and bold claims were vindicated when Jesus rose from death.(Rom 10:9-11)
• With this understanding, accept Jesus as your absolute Lord. A warning though: thinking, “I may disagree with Jesus on homosexuality (if He condemns it) or other cultural fads” is likely not enough. If you decide now to only invite God's co-driving on a restricted basis, then you'll remain liable to wreck your car in heaven, which is unacceptable to a perfect God whose goal is to ultimately eliminate all evil. God can't keep you for the new Kingdom if you don't ultimately choose to submit fully. So while Christians in weakness can regretfully choose to sin time and again before the New Kingdom, at their highest ultimate decision level they see Jesus as their master and habitually repent. And Jesus says, “no one can serve two masters” (Mt 6:24).

If you wish, you can also meet God in prayer. He hears you! There is no formula, but you can pray something like this:

“Lord, I know that your righteous frustration with me for my sins is great, but I know your loving-kindness is as well. You have promised to grant forgiveness to the undeserving sinners like me if they repent and turn to you. Your perfect goodness ensures this promise is trustworthy, and so this is precisely what I'm doing. Forgive me and take control. I want to submit to your will entirely, now and through eternity.”

As you rest in this decision, you can praise and thank God in complete confidence. As He promised, your sins are covered. Of course, the Christian life does not end here. As mentioned above, God spiritually indwells believers, and so will constantly be transforming you into someone with a more Christ-like view of the world, and a more Christ-like character who can hate and overcome sin more and more easily. You should immediately find a way to be fellowshipping with others who have made the same decision because God is bringing the world a taste of His kingdom through you and others as you love each other. You should also get baptized as Jesus commanded, to publicly express your affiliation with Him in His death and resurrection. (Failing to get baptized as a Christian is inappropriate, like marriage without a wedding ring.) Also, the Christian life can be hard, and you may even suffer extreme persecution. However, as Jesus spiritually abides in you, you will find a fellowship with God and supernatural joy that kept early Christians singing praise to God even as they were being martyred. Have confidence in God's promise to you. Jesus is Lord, conqueror of death, holy destroyer of sin. His new Kingdom, the final stage of this grand plan, is our hope and it is on its way for you and me. :)