Stan Larkin of Michigan, age 25, has led a fairly normal life - except that for nearly two years, he didn't have a heart in his body. Last month, he finally received a heart from a donor. But for over a year and half before that, he had no human heart at all! Instead, he had a pump, connected to a machine that he carried around in a backpack, which circulated his blood.
The entire story is amazing. It also powerfully illustrates why brain death should be rated as death - with the consequence that the organs of people who are brain dead should be used to save the lives of other people.
Stan Larkin's story shows that the heart, as incredible an organ as it is, has nothing to do with housing our identity or our soul. It's just a sophisticated blood pump - nothing more, nothing less. When Stan didn't have a heart, just a machine in a backpack, he was no less of a person. And when he received the donor's heart, he didn't "become" the donor.
Due to the wonders of modern technology, enabling scenarios that never occurred before in history (and are thus not addressed in halachic sources), the same thing could happen with pretty much any of the body's organs. You can switch them out for artificial replacements, or you can transplant them from other people. It's amazing medical technology, but it has absolutely no consequences for their identity or their soul.
Except for the brain! You can't replace the brain with a machine. And you can't currently transplant one from someone else - but when technology eventually makes this possible (as it presumably will), there will most certainly be crucial consequences for the person's identity and soul. If, a hundred years from now, Stan Larkin Junior loses his brain, and has it replaced by that of a donor, then Stan Larkin Junior has ceased to exist, and the donor has taken over his body. The only way that Stan Larkin Junior can remain existing without a brain is if by then it is somehow possible to download the "software" of the brain onto a computer (which seems highly unlikely).
It's clear that a person's identity and soul is fundamentally rooted in his brain, not in his heart or any other organ. The heart is no more significant than any other organ. It can be replaced by a machine in a backpack. It's only the brain that is crucial to personhood. When the brain is no longer present, the person has passed on. And this gives us a unique opportunity to use their organs to save the lives of several people.
If you haven't yet signed up to be an organ donor, please do so today, at www.hods.org.