The following was written in partial fulfillment of the requirements of Dr. Steve McKinion's Christian Theology II class at Southeastern Baptist Theological Seminary.
When God placed Adam in the Garden of Eden, he told him he could eat freely of any fruit in the garden except one: the tree of the knowledge of good and evil. If he ate from that tree, however, he would die the very day he ate of it (Genesis 2:17). When, in Genesis 3, Adam and Eve ate the fruit of the tree of the knowledge of good and evil, however, they did not die—at least, not physically. Indeed, Adam lived to be over nine hundred years old.
What, then, did God mean when he told Adam that he would sure die the very day he ate of the tree? Did he lie, or make a mistake, or change his mind after the fact? Plainly put, no: none of these are true. Rather, all of them mistake the nature of the death entailed in God’s word to Adam. The death Adam immediately experienced was not physical death but spiritual death. Physical death was a consequence—a symptom, as it were—of his spiritual death.
This spiritual death was multifold, and we see the various elements of it traced out in the explanation of the fall given in Genesis 3. First of all came separation from God. Rather than being in right relationship with the creator, Adam now needed restoration. Whereas he had enjoyed fellowship and relationship with his maker, now Adam experienced fear at the thought of encountering him, so that he hid himself when God came walking in the garden in the cool of the day. The rest of the Old Testament traces this theme out in great detail; it is constantly asking the question, “How may these unrighteous people come before a holy God?”
Second, God removed Adam from the means of grace he had supplied to sustain his mortal body. He had provided a tree of life from which Adam could eat so that his body would go on living without fail. After the fall, Adam was removed from this supply, and so his body began to fall apart. He began to experience the first phase of physical death: aging and decay. He no longer had access to the supernatural sustenance he required not to die.
Third, he immediately experienced relational brokenness. The previously holy and mutually delightful relationship he had experienced with his wife would now be characterized by mutual blame and recriminations. Likewise, his sons would not be loving brothers: one would kill the other. No more would he live in a world characterized by peace and harmony, but one shaped by conflict and war.
Of all of these, though, it was the first that was most important and deepest. Adam’s separation from God was at the root of all the other problems he now faced. It was the lack of God’s spirit in him that led to his physical death. It was the lack of God’s presence in their midst, and the brokenness of his image in them, that led men and women to be in conflict rather than mutually supporting one another. With this separation came a warp in the character of humanity that comprised the final part of Adam’s immediate death: no more would his will be ready to obey God. Instead, he (and all his descendants) would be quick to turn aside to go against the grain of God’s universe. Given the opportunity, all would sin, and no one would turn away from sin without God’s intervention.
Thus, Adam did experience death the very day, indeed the very moment, that he ate of the tree of the knowledge of good and evil. The death was more profound and more horrifying than physical death alone would have been, though, because it was a death that stretched to every point of his life, from his family and the tasks with which God had entrusted him, to his very connection with God. Everything became broken in him, and he no longer knew God. In gaining the knowledge of good and evil, he lost the knowledge of the one of whom knowledge matters most.