Impassibility refers to the impossibility to suffer and die.
God drew man's body from the elements of the earth by means of the evolutionary changes He brought about in the animal kingdom. He gave man an immortal soul bestowing on him the gift of integrity which he had not given the animal kingdom. But, the first man and woman rebelled against God thereby losing the soul's unifying power which it had when fully oriented toward the living God. At that moment, Adam and Eve became subject to the biochemical dynamics of the animal kingdom which includes suffering and death.
The loss of control of the soul over the body is well expressed in the book of wisdom:
"The corruptible body burdens the soul
and the earthen shelter weighs down the mind
that has many concerns." (Ws (9:14-15)
Terrorist attack:World Trade Center
Sep. 11, 2001:c. 2,823 died.
So, now our bodies are ravaged by disease,
maimed and destroyed by accidents and the powers of nature, tortured and killed
by the hatred of men. Most of us, however, die of aging. Aging
is caused by genetic errors which occur when body cells replicate. Despite
this, there is an innate
desire in man to live forever, not to suffer
sickness or death, because God intended man to be immortal from the beginning.
CHRIST THE CAUSE OF BODILY IMPASSIBILTY
The Son of God by becoming man took on our corruptible nature and became the cause of our incorruptibility. St. John tells us that with the death of Lazarus, Jesus told his sister Mary, "Your brother will rise" (Jn 11:23) and she retorted: "I know he will rise...on the last day". Jesus told her, "I am the resurrection and the life...." Jesus not only affirms her belief in the resurrection but He points to himself as the power which would bring this about. And because of his fidelity to the Father's will, his body remained incorrupt in the grave and was transfigured never to die again.
MEANING INCORRUPTION VS. IMPASSIBILITY
What causes corruption? The soul is always in act in order to actualize the body but is unable to fully activate the body. And so, the body is subject to form changes which eventually loosen the grip of the soul upon it thus causing death.
The soul in heaven is perfectly subject to God as will the body be now subject to the immortal soul so that it will be impossible to the body to undergo any change contrary to the disposition of the soul. We saw earlier that the spiritualized body can pass through solid matter and so should even a mountain fall upon us, it cannot harm the body. And in Revelation we read, "They will not hunger or thirst anymore, nor will the sun or any heat strike them." (Rv 7:16) Because our spiritualized body will be dynamically altered by the disposition of the soul, it will have power over nature rather than nature having power over it.
On the other hand, the soul of the damned is only able to fully activate its body only with regard to incorruptibility but will not have the gift of impassibility, that is, freedom from suffering. Their bodies will be a heavy burden to them, suffer endless pain and torment, burning forever in the fire without being consumed.