You're conveniently leaving out the full name. It was the Tree of the Knowledge of Good and Evil. Can't have one without the other. We could have lived in God's paradise or live in a world where we choose between good and evil. Satan(the talking snake), tempted Eve and then Eve convinced Adam to disobey God. Satan's sin was pride as well, and since fell, he couldn't stand for God's favorite creation to be in good standing. So he influenced Eve to disobey and then Adam followed suit. Once again, God nor Satan can make us do anything. We choose to follow one or the other. Everything comes down to our choices.