Why I Signed Up To Be An Organ Donor
I am normally loath to publicize my opinion on topics that I have not thoroughly researched. And I have not thoroughly researched the topic of organ donation. But there is no "shev v'al taaseh" on this topic, since lives are potentially at stake. And although I have not thoroughly researched the topic, I do think that the basis for my decision to sign up with the Halachic Organ Donation Society has weight.
First, I should disclose that I have personal experience with the loss of an immediate family member (my father) which involved difficult end-of-life decisions, as well as a friend whose life was saved via receiving a liver donation. While some might argue that this means I am emotionally biased towards saving lives, I think that it means that I have a better understanding of the value of life than someone who has never experienced real life-and-death scenarios.
My reasons for considering that those advocating for the halachic permissibility (indeed, preferability) of organ donation are correct, are as follows:
Those who claim that organ donation is halachically prohibited are basing themselves on the idea that a brain-dead person is not truly dead (and thus his organs cannot be recovered), which in turn is based on various inferences from the Gemara that only cardiac death is considered true death. But based on my research, it is abundantly clear to me that Chazal, consistent with standard belief in the ancient world, mistakenly believed that the mind and soul are housed in the heart and kidneys, not in the brain. It is for this reason that Chazal considered the status of the heart to determine whether one is alive or not. Now, ordinarily, I follow the approach of those who say that halachos canonized by Chazal are binding even if based on mistaken beliefs about the natural world. Being an Orthodox Jew means subscribing to the halachic authority of Chazal. But I would not adopt that approach in this case, since (a) it is a matter of saving lives, and (b) it was never formally canonized that cardiac death rather than brain death defines true death.* (My impression is that those who do not accept brain death will not declare that Chazal and Rishonim had a mistaken understanding of physiology in this area; I would be very interested if someone can demonstrate otherwise.)
Another reason why it seems to me that one should be an organ-donor is that it is a case where fundamental Torah values take precedence over technical halachic discussion. I recall learning somewhere (perhaps someone can recall the source) that if one is stranded on a desert island, and the choice is to eat crabs or one's dead co-travelers, then even though from a strictly halachic perspective there are less prohibitions involved in eating a dead human being, nevertheless fundamental Torah values dictate that one should eat crab instead. Similarly here; when we are talking about saving multiple lives at the "cost" of someone who is effectively dead, I think that fundamental Torah values cry out to save those lives - and I think that if Chazal were alive today, they would certainly agree.
Finally, someone that I know and respect greatly has written on this topic at Rationalist Medical Halachah. His analysis appears sound; I know him to be scientifically knowledgeable (he is a physician) as well as a talmid chacham; I trust his honesty; and we share the same epistemology, i.e. the rationalist approach.
You can learn more about being an organ donor, and sign up, at www.hods.org.
* Note that the Gemara speaks about cessation of brain function such as breathing, and not about the brain per se.