In The Problem of Pain, Lewis wrote:
“The human spirit will not even begin to try to surrender self-will as long as all seems to be well with it.
Now error and sin both have this property, that the deeper they are the less their victim suspects their existence; they are masked evil.
Pain is unmasked, unmistakable evil; every man knows that something is wrong when he is being hurt …
God whispers to us in our pleasures, speaks in our conscience, but shouts in our pains: it is His megaphone to rouse a deaf world …
No doubt pain as God’s megaphone is a terrible instrument; it may lead to final and unrepented rebellion.
But it gives the only opportunity the bad man can have for amendment, it removes the veil; it plants the flag of truth within the fortress of the rebel soul …
Suffering is not good in itself. What is good in any painful experience is, for the sufferer, his submission to the will of God …
… If tribulation is a necessary element in redemption, we must anticipate that it will never cease till God sees the world to be either redeemed or no further redeemable.”