When God made mankind, He had a specific idea in mind. He did not want to make another race of angels—glorious, holy, powerful servants who, even in rebellion, were destined to do His work and fulfill His purpose. He did not want animals—creatures that would bring Him pleasure and display His glory and creativity—perhaps even respond to His goodness—but could not begin to fathom Him. He wanted children (Luke 3:38). Beings both made out of the raw materials of His creation and indwelt with His own breath (Genesis 2:7).
What is the tree of the knowledge of good and evil?
That is what Adam and Eve were. Created children, born into a specific place in the divine hierarchy (Hebrews 2:6-8), given a purpose that would most exemplify the characteristics of God that He shared with them (Genesis 1:28). They were to care for His creation, use their own creativity, and live rich, content lives in an easy harmony with God as their will aligned with His. Adam and Eve were sinless, but they were also innocent. They had no evil in them, and their characters were untouched by exposure to evil. They were put in a place perfectly designed for their personalities. All their needs were met; they had companionship, communion with God, work, and food.
But communion without choice isn't communion. Friendship without freedom is akin to slavery. A beautiful garden, specially made to bring joy and fulfillment, is still a prison if it doesn't have a gate. It's a gilded cage. It's been said many times that God did not create mankind to be puppets. It was not His will to determine our every action. Instead, He did something much more powerful and much more dangerous. He created beings who were endowed with His will and character, but were not controlled by Him.
And then He put a gate in the cage of paradise. He put in the most banal, dismissible gate possible—a tree in the middle of a garden (Genesis 2:9). In the midst of a forest of fruit trees and playful animals and beauty, He placed one tree and said, "Don't eat." Adam and Eve were surrounded by food. They had everything they needed. It would have been like being told an entire car dealership was yours, but you couldn't drive one car.
The tree wasn't evil. It wasn't cursed or supernaturally imbued with sin, and the fruit did not contain some special ability to impart knowledge of good and evil. But the act of taking the fruit and eating it was an act of rebellion. It was taking something made with God's character and acting contrary to that character. The result was a defilement of that character. Humanity turned from something designed to align with God's will to something that desired its own. "Sin entered the world," but it also entered into the standard operating procedure of those who sinned. Adam and Eve understood evil because they drew it into their hearts.
Paradise without the ability to leave is just a pretty prison. God didn't want prisoners or slaves. He wanted people. Foolish enough to walk away, but loved enough to rescue (John 3:16).
Original sin - What is it?
Spiritual death - what is it?
Why did God create humanity?
What does it mean that humanity is created in the image of God?
Does life have meaning?
Truth about Creation