Here is an answer I gave in another forum, slightly revised
Apart from evil that arises out of fallen human nature, we should recall that when man fell, nature itself was affected. Whereas before it was perfect, nature also became fallen:
I consider that the sufferings of this present time are not worth comparing with the glory that is to be revealed to us. For the creation waits with eager longing for the revealing of the sons of God; for the creation was subjected to futility, not of its own will but by the will of him who subjected it in hope; because the creation itself will be set free from its bondage to decay and obtain the glorious liberty of the children of God. We know that the whole creation has been groaning in travail together until now; and not only the creation, but we ourselves, who have the first fruits of the Spirit, groan inwardly as we wait for adoption as sons, the redemption of our bodies. For in this hope we were saved. Now hope that is seen is not hope. For who hopes for what he sees? But if we hope for what we do not see, we wait for it with patience. (Romans 8:18-25)
This is where diseases and natural disasters, as well as decay and death itself come from. Thus it will be with us until the Second Coming when there will be a new heavens and a new earth (Revelation 21).
One way to look at it is this. It is indisputable by everyone (except maybe Buddhists, who think it’s an illusion) that there is suffering going on in this world. And it’s a given that at some time in our lives, most of us will undergo some type of suffering. Many religions and philosophies have tried to answer the question of why there is suffering in the world with answers ranging from the Buddhist approach, to the atheist, who says there is no purpose or meaning in anything, including suffering.
To me, the Catholic Church has the only comprehensive (as well as rational and biblical) approach to this in her teaching on redemptive suffering.
Basically the Church teaches that the unavoidable suffering in our lives (our particular “crosses”) can be transformed by Christ and joined with his own sufferings on the Cross toward the salvation of others. This is what is meant when Catholics have traditionally “offered it up.” This is based most explicitly on Paul’s mysterious words in Colossians 1:24: “I complete in my body the sufferings that are lacking in the sufferings of Christ.”
This is not to say that Christ’s death on the Cross was in any way insufficient (it wasn’t). But it does say that when Christ tells us we must pick up our cross and follow him, there is a purpose and a meaning behind that suffering, and that it is not mindless or in vain.
Some pertinent Catechism references are:
307 To human beings God even gives the power of freely sharing in his providence by entrusting them with the responsibility of “subduing” the earth and having dominion over it. God thus enables men to be intelligent and free causes in order to complete the work of creation, to perfect its harmony for their own good and that of their neighbors. Though often unconscious collaborators with God’s will, they can also enter deliberately into the divine plan by their actions, their prayers and their sufferings. They then fully become “God’s fellow workers” and co-workers for his kingdom.
618 The cross is the unique sacrifice of Christ, the “one mediator between God and men”. But because in his incarnate divine person he has in some way united himself to every man, “the possibility of being made partners, in a way known to God, in the paschal mystery” is offered to all men. He calls his disciples to “take up [their] cross and follow [him]”, for “Christ also suffered for [us], leaving [us] an example so that [we] should follow in his steps.” In fact Jesus desires to associate with his redeeming sacrifice those who were to be its first beneficiaries. This is achieved supremely in the case of his mother, who was associated more intimately than any other person in the mystery of his redemptive suffering.
*Apart from the cross there is no other ladder by which we may get to heaven. *[St. Rose of Lima]
1508 The Holy Spirit gives to some a special charism of healing so as to make manifest the power of the grace of the risen Lord. But even the most intense prayers do not always obtain the healing of all illnesses. Thus St. Paul must learn from the Lord that “my grace is sufficient for you, for my power is made perfect in weakness,” and that the sufferings to be endured can mean that “in my flesh I complete what is lacking in Christ’s afflictions for the sake of his Body, that is, the Church.”
I couldn’t possibly do justice to the sublimnity of this teaching, but here is an article which may help you:
rosary-center.org/ll49n2.htm
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