Satan made a seemingly gentle suggestion against God's word and work, first by presenting them in a negative light. God had spoken to Adam and Eve, giving them His word. They had gathered much about the mind and personality of God because of what He said.
In addition, they could see with their own eyes a great deal about God's person, personality, and mind by what He had made. They were in a beautiful garden, which reflected the mind of God. They could see the beauty of His mind, and how His mind provided things beautiful and delightful to enjoy. They knew a great deal about the mind of God simply from what they were able to observe.
By making the challenge the way Satan did, he first made them mildly skeptical about God's love, asking them, Does God really love you?
Second, he made it seem as though obedience to God was, in reality, servility. He made them begin to feel as though God's way was restrictive; that He was holding back good things from them. This thought naturally led them to think much more could be obtained from life if they just followed their body's and mind's natural inclinations.
Third, he played his trump card: Not only would they not die, but they would be in control, free to determine right and wrong. In short, they would be equal to God!
Satan successfully brought them into a spirit of competition against God, resulting in the enmity described in Romans 8:7. He indirectly lied about God Himself, and he directly lied about the penalty, giving them misinformation about the reward.
He did tell them the truth, that their eyes would be opened and that they would not immediately die. Their eyes were opened, and they now looked at things through the twisted perspective, seeing evil in everything. From innocence, they became ashamed of their nakedness. The effect began immediately.
This is important because right thoughts precede right actions; right thoughts determine the release of proper emotions. Our thoughts express themselves even in our most casual relationships, in daily work, and most importantly, in our intimate relationships in our home and family. Most of all, they express themselves in our relationship with God. False beliefs about God and His purpose for man are far more destructive than alcohol and drugs. They confuse, divide, and bring on warfare.
Satan's lies, his counterfeits, and his devices are usually so subtle that only a trained mind can discern them. God teaches us to be able to see. He trains us to be able to spot the ploys, contrivances, and stratagems of our enemy so that we can overcome and defeat him.