There was indeed a literal Adam and Eve, garden of Eden, and tree of the knowledge of good and evil (Genesis 2:15–17). Adam and Eve did literally eat a piece of forbidden fruit and thereby introduce sin and death to mankind. Whether there was something in the fruit itself that was harmful is largely irrelevant. It is not so much the actual fruit that brought death as it was Adam and Eve's disobedience to God.
Was Adam and Eve's sin really about eating forbidden fruit?
God had given Adam dominion over all the animals and access to all the trees in the garden of Eden save one. God did this not because He desired to keep Adam and Eve from any good thing, but to test their reliance on Him for all good things, and to test their obedience to, faith in, and love of God and His Word. Apart from meaningful choice, there is no depth of relationship. There would be no true love between God and humans if people were not free to choose against God. Forbidding the fruit from the tree of the knowledge of good and evil was not an act of cruelty; it was an offer for true relationship based on free will.
When Eve believed Satan's lies and Adam followed her, the couple chose to trust their own independent reasoning and sense perception over God's Word (Genesis 2:15–17; 3:1–7). They ate the fruit because they saw it was good for food and pleasing to the eye, despite God's command and His warning about the consequence. They did not honor God for who He is and instead treated themselves as their own gods.
So, was Adam and Eve's sin really about eating the forbidden fruit? Yes, in the sense that the fruit was the object by which they demonstrated their choice against God. In eating the fruit, they gained experiential knowledge of evil. Their sin immediately resulted in spiritual death and shame. They were separated from God and all of humanity would be born in sin and separated from God (Romans 3:10–12; John 3:16–18; Ephesians 2:1–10). They also experienced a break in their relationship with one another and a break in their relationship with creation. The fall has affected our entire world.
But Adam and Eve's sin did not change God's character or His heart. He knew even before creating them that they would sin. Yet He still chose to create, out of love. He also provided a means by which all people can be saved from sin—Jesus Christ. Romans 5:19 tells us, "For as by the one man's disobedience the many were made sinners, so by the one man's obedience the many will be made righteous." Jesus is referred to as the second Adam. He is fully God and He took on human flesh, becoming fully human as well. Jesus Christ obeyed God perfectly and paid the sin-debt we have incurred through His death. He conquered sin and death through His resurrection. Any who put their faith in Him can be free from condemnation (John 3:16–18). In Adam we fell under the curse of sin and death; in Christ we are raised to eternal life (John 3:36). Truly, the sin of Adam and the obedience of Christ are two of the most cosmic events in the universe, affecting the entire human race.
What is the tree of the knowledge of good and evil?
What is the tree of life?
What is sin?
Does everyone inherit sin from Adam and Eve?
How can I be saved?
Truth about Creation