From
catholic.com/magazine/articles/before-sin
The Two Trees
The recreation of the world is a long way off when Adam and Eve trudge sadly out of the Garden, but already, in the final lines of Genesis 3, salvation is being prepared. There are two trees growing in Eden: the tree of the knowledge of good and evil and the tree of life. Adam and Eve eat from the first, but are prevented from eating from the second.
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It is interesting to note that there is no tree of death or tree of evil within the garden, only the tree of the possibility of evil. When Adam and Eve eat they interiorize that potential and make it real. This creates a new relationship between man and Creation. Suddenly, all of the things that were “good” in the beginning have potential for evil. That makes the image of a tree particularly apt because of the countless branches of knowledge which in our fallen condition represent a genuine danger:
Spiritual knowledge may now be used for sorcery.
Scientific knowledge may be used to exploit and destroy.
Moral knowledge may be used to censure and condemn.
Aesthetic knowledge may be used to make evil look attractive.
Every field of human endeavor is poisoned because humanity now knows not only how to use knowledge for the greater glory of God, but also how to use it in disordered and damaging ways.
The second tree is the antidote to this problem, but it is also dangerous. When God banishes Adam and Eve from the garden and the tree of life, bodily immortality is no longer possible. It was an act of mercy that he did so. Those who choose to love and serve God could hardly find endless life in a valley of sorrows desirable; those who reject God must not be allowed to grow in their evil indefinitely or to continually inflict harm on others without ever being subjected to justice. God posts at Eden’s gates “the cherubim, and a flaming sword which turned every way” (Gn 3:24). Eden is permanently closed to man. At the same time, however, the tree of life is being prepared and the fruit of salvation is ripening in its branches, for its hour has not yet come.
It is not by accident that the tree of life appears constantly in world mythology. The tree spreads out her branches across the galaxies, and stars spin like apples from her boughs. All life, all Creation, springs from the root of this tree, and its sap is the water of life. The tree is an image of the entire created order, a single, unified organism in which all things are reconciled and made one.
It is, of course, the cross, and its fruit is Christ crucified. We eat of its fruit each time we participate in the mystery of the Eucharist. It is the pillar on which the world is made, the source of all life, ordained from the beginning, the sacrifice which God had prepared to redeem and renew his Creation.