No, I meant, can we 100% say, that if someone has cancer, or dies from cancer that sin in their lives are the cause? No tripping intended. I thing you answered this above.
We will agree though, that if what happened in the garden of eden did not happen, these issues of illness probably would not have received the air-time it gets. AS you say, cancer from too much sun - so if that happens to the farmer who is permanently in the field, then it surely was not due to sin, or lack of faith, but simply as it's part of life that can happen to you.
So this is something bad that happens to someone, without him necessarily deserving it - especially if we know this man is a passionate follower of Christ yielding much fruit.
So what now? How is this bad thing coming over this person's life? Surely God should have stopped it?
But He did not, so, this bad thing happened for a reason, nothing is coincidence. Therefore God allowed it to happen, even though it was bad. To show His glory? To show a miracle to an unbeliever friend/neighbour? To test the person/s? To grow his faith? To bring him to another place where He wants him? Who knows, but it will be to the glory of the most high God.
I do believe it is God's will to heal any illness - but, it's on His terms, not ours.