CBS News Correspondent Mark Phillips has been searching for the facts on Pope John Paul II's health and its impact on papal politics and policy.
With his slow, painful steps and repeated gestures of apparent discomfort, the poor health of this almost 80-year-old pope is an open secret.
The pope's own doctors won't openly discuss his ailments but Dr. Sergio Arena says they are common knowledge.
Most of the problems can be traced back to the 1981 attempt on the pope's life, to the large tumor removed from his abdomen and to the fracture from a fall that never completely healed.
But it is the trembling of the pope's left hand, a sign of Parkinson's disease, that is the greatest concern.
Specialists like Dr. Fabrizio Stocchi, who has seen the pope's medical file, say that his disability will inevitably worsen and that dementia is even a possibility. But he adds, "Parkinson's disease is not a disease that leads people to die so he won't ever die from Parkinson's disease."
However debilitating his ailments, though, Pope John Paul sometimes seems to carry on through force of will alone. He may seem frail but in the words of one Vatican source who should know, he has the heart of an ox.
And he has the determination to match, which worries some in the church faced with the possibility of a mentally deteriorating but physically surviving pope.
"There is a story, which I'm inclined to believe, that the pope has written a letter which says, 'If I become incapable of discharging my duties, my papacy is to be considered at an end.' But who is to decide that?" asks John Wilkins, editor of the Catholic newspaper The Tablet.
Even now the Vatican has become fertile ground for intrigue.
According to John Cornwell, a writer on Vatican affairs, a power vacuum has been created in which factions both on the right and on the left are in very tough competition to make their voices and their influence felt.
Because of his illness and his age, Pope John Paul's famous firm grip on papal power is weakening.