How can Adam be free to eat the apple when he was created to eat the fruit?
What makes you assume Adam was "free"? Whatever it is that you mean when you say "free", it is obviously not compatible with Adam being ordained to eat the fruit, but then how can you assume Adam had this type of freedom?
Calvinists believe the Bible means what it says. What do you think the Bible means when it says that before the foundation of the world God had planned to slay his Son? It does say that, and I've already quoted the verse.
All who dwell on earth will worship it, everyone whose name has not been written before the foundation of the world in the book of life of the Lamb who was slain (Revelation 13:8).
Don't just ignore what's obvious in the verse just because there are some hard things about it to understand (such as what the beast is in Revelation). We can draw some conclusions from this verse without even understanding the difficult things. For instance, we know God has a book with names in it. It doesn't matter if it's a physical book, which I grant to you it probably isn't, or if the "book" is metaphorical. What matters is this verse says God has a list of names and if your name is in this list you will not worship the beast, whatever the beast is is irrelevant. And the Lamb was slain for the names of the people on this list. When was the book written? This verse says, "before the foundation of the world." So before creation, God already knew that he would slay his Son. God could have not created the world. Or he could have created it a different way; in such a way that his Son would not have to be slain. But he did it this way, knowing already that his Son would be slain, and he did it that way because he wanted to. He planned it. It doesn't matter how you conceive on the immediate causality. If you know how something is going to turn out because of what you do and you know that later you'll do something else, and you want to do that, so you do it, we call that a plan. God created a world where sin would exist and his Son would be slain because he wanted to.
There are plenty of other examples in the Bible where we are told God planned specific sins. Would you deny that the murder of Jesus at the hand of the Romans and Jews was a horrendous evil? Would you deny that the Romans and Jews who murdered Jesus were acting sinfully? But the Bible says they killed him "according to the definite plan and foreknowledge of God" (Acts 2:23). And two chapters later it says it again,
Truly in this city there were gathered together against your holy servant Jesus, whom you anointed, both Herod and Pontius Pilate, along with the Gentiles and the peoples of Israel, to do whatever your hand and your plan had predestined to take place (Acts 4:27-28).
God planned Jesus' death. It can't get any clearer than that. Yet the Jews and Romans who participated are still responsible for their sins.
Another great example is Joseph's being sold into slavery by his brothers. Joseph said to them, "You meant evil against me, but God meant it for good" (Genesis 50:20). There was no doubt in Joseph's mind that behind his brother's wicked plans was God's good plan.
Or Job, who after all ten of his children were killed by Satan, fell to the ground and said, "The LORD gave, and the LORD has taken away; blessed be the name of the LORD" (Job 1:21). Do you think Job was wrong in attributing what Satan did to God's ultimate plan? The writer of the book didn't, for the very next verse says, "In all this Job did not sin or charge God with wrong."
Or Peter, who had a very similar story to Job. Satan came to God and said, "Let me sift Peter like wheat," and God said, "Alright." But look what Jesus said to Peter, "But I have prayed for you that your faith may not fail. And when you have turned again, strengthen your brothers" (Luke 22:32). That's absolute sovereignty talking. Jesus did not say, "
if you turn," Jesus said, "I have seen to it that your faith may not fail utterly,
when you have turned strengthen your brothers." And when Peter objected and said, "I would never deny you; I would die for you." Jesus did not say, "Well you do have free will, so if you try hard enough you can overcome what my Father has planned." Jesus said, "I tell you, Peter, the rooster will not crow this day, until you deny three times that you know me" (Luke 22:34).
Or Naomi, who after her husband and two sons died said, "The Almighty has dealt very bitterly with me. I went away full, and the LORD has brought me back empty" (Ruth 1:21). There was no question in her mind that her husband and sons were dead because God had planned it.
Or Pharaoh, who refused to let the Israelites go; why? Exodus 4:21 says, "the LORD said to Moses, 'When you go back to Egypt, see that you do before Pharaoh all the miracles that I have put in your power. But
I will harden his heart, so that he will not let the people go.'"
Proverbs 21:1 says, "The king’s heart is a stream of water in the hand of the LORD; he turns it wherever he will". And that applies to good kings and bad kings.
Mark 1:27 says, "He commands even the unclean spirits, and they obey him." When Jesus says, "Satan you can inflict Job will all kinds of sores and painful ailments, but do not lay a hand on his life," Satan does not frustrate Jesus' plans with his free will and kill Job. Satan obeys.
Daniel 4:35, "He does according to his will among the host of heaven and among the inhabitants of the earth; and none can stay his hand or say to him, 'What have you done?'"
Isaiah 45:7, "I form light and create darkness, I make well-being and create calamity, I am the LORD, who does all these things."
Amos 3:6, "Does disaster come to a city, unless the LORD has done it?"
Matthew 10:29, "Are not two sparrows sold for a penny? And not one of them will fall to the ground apart from your Father." Even birds that aren't worth more than a penny, not a single one dies unless God wills it.
Proverbs 16:33, "The lot is cast into the lap, but its every decision is from the LORD." Or to put it in modern-day terms, "There is not one dice roll in Reno that isn't governed by God" (John Piper, I think; maybe Sproul?). That's what Proverbs 16:33 says. God plans every win and every loss in Vegas.
There are so many verses that teach that God is absolutely in control of all things, whether it be weather or death or sickness or famine or poverty or riches or wickedness or righteousness, God plans it. These verses aren't lies. They're there because it's true.
Do you know what sovereignty is? Sovereignty is Isaiah 14:27, "For the LORD of hosts has purposed, and who will annul it? His hand is stretched out, and who will turn it back?" God is in control. No one frustrates his plans. God did not create us hoping we wouldn't sin and then get his plans of a perfect world frustrated by men with free wills.
God planned that we would fall so that his Son could die for us and get the glory that only a Redeemer can. "God shows his love for us in that while we were still sinners, Christ died for us" (Romans 5:8).
One thing people struggle with as they're learning about Calvinism is this assumption that if God planned our sin, we're not responsible for it. But that's not what the Bible teaches. The Bible teaches that somehow, and it is a mystery, I do not understand it fully, but somehow God has done things in such a way that we are still responsible for our sins even though he planned them to serve his good purposes.
I saw another poster here (I think it was GrinningDwarf) pose this question to someone else, and I'll pose it here for you. If this is true, that God has planned even our sins, why does he still find fault? For who can resist his will? How would you answer that question?
Don't lose this question in the rest of my post because the apostle Paul was asked the very same thing, and I'd really like you to try to answer it before reading how Paul answered it. Don't look it up. Try to answer it to the best of your ability. Answer it as if someone who was struggling with Calvinism had come up to you and asked you, "Why does God still find fault? For who can resist his will?" What would you say to them? Then compare your answer to Paul's answer and see how they line up. I'll tell you where Paul answered it after you think about it some.
I know this is hard, but please give it some good honest thought. The biblical evidence for God's sovereignty in all things is overwhelming. Calvinism isn't just a philosophical discussion on whether God could create men with free will. Calvinism is what the Bible teaches, and that's the only reason I ever accepted Calvinism. But I can promise you, it has not been a gloomy acceptance. It has been a joyful acceptance, and I am glad to serve a God whose purposes cannot be frustrated, who ordains that all things should come to pass, who upholds the very foundations of life with his very thought. The God of the Bible; the sovereign Lord over all creation, is a glorious God worthy of all praise and adoration.
May he open your heart to his eternal truths,
Nathan
(Much of this post is nearly a direct quote from Piper's sermon
"Where Is God? (UCF)". I highly recommend listening to it.)