When man fell. He took of the tree of the knowledge of good and evil in his attempt to be like God. He forsook the life he lived by attempting to have life using his knowledge of good and evil.
The man was subsequently sent out of the garden and a flaming sword to keep him out put in place. To get in, you had to die.
The man had two sons - Abel and Cain. A time came when they brought gifts to God. One, knowing there was nothing in him that was good, gave the life of another - the firstling of his flock as a sacrifice. The other, gave out of his toil, the fruit of the ground. God rejected one and accepted the other, indicating life was not by our own toil and mind.
Later, we come to a man called Abram. He is later called Abraham. While Abram, he receives a promise of God but attempts to fulfil it in his own strength with a slave woman - Hagar and brings forth Ishmael. When he is Abraham, God gives him what He promised at a time when it is impossible for him to have children in his own strength. We see Isaac and Ishmael, the two men again - one of life (promise), one of labour of man.
We see two men - Abram and Abraham separated by a cross, one brought to his end to establish another's life.
We also see two men in two women - Sarai and Sarah, Hagar and Sarah. One living by promise, by the life of another, another living by toil and labour and self knowledge.
Later Isaac, has two sons - Esau and Jacob. It is important to note at one point God says "Jacob I loved, Esau I hated".
Esau, sold his birthright, for a morsel of bread. He was a hunter, ever on the prowl for things. Jacob, was always in the house ( a picture of a man dwelling/ abiding in God) and from this, he got the blessing. One lived by rest, another lived by strife.
Later, Jacob gets a new name - Israel after struggling with God and being injured in the hip. He becomes lame and can only walk in picture assisted by God. We see the two men again.
Later on, we see the two men in David and Saul. One annointed chosen by God, another by people because of his own attributes.
We can go on and on and see pictures of these two men but they all point to the same image - Adam a living soul, who could use strength, wisdom, understanding of his own to live (and who was rejected), and Christ, who is a picture of the life of God living who is accepted ("This is my beloved Son, in whom I am well pleased).
When we come to the cross, there is a dividing. At the cross, all life finds death. However, those in Christ are regarded as the resurrected, those without, are still as dead. There are those living by the life of Christ, others by the life of Adam. The difference between the two of them is notable. One attains to self. The other to another. One produces death, another life. One is full of strife, another peace.
Not to be confused between wrong and right, because Adam knows both of these and tries to manufacture good in his own strength and avoid bad in his own strength. In Christ, Adam is dead, Christ is alive. He is the only one living.
In the end, in the sense of men - two exist. All we do is either of one or the other. Self or another. It applies to everything. There is nothing this does not touch in the view of God. In the end, he rejected Esau, Adam, Saul, etc all pictures and accepted one - who was the original plan of living, that we should live by His life and His alone.
In a sense Paul sums this up with this beautiful verse -
Gal 2:20 I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.