N0mesorah
The second half of your post sounds right, the first half is confusing.
“I understood that the heart could be functioning mechanically – not reflexively”
I am not sure what you mean by either of those terms. The heart can beat independently of the brain. In fact they have done studies where a heart placed in proper solution of glucose, potassium, with oxygen being pumped etc can keep on beating in the absence of any brain activitiy. This is becasue the signal for he heart to beat does not come from the brain, but rather from specialized cells in the heart itself, that “tell” the heart to beat. This is known as the pacemaker cells or the SA node. Of course the brain (and spinal cord) do send signals to the heart to speed up or slow down as needed but in the absence of these signals ie even with complete severance of the brain and spinal cord from the body the heart will keep beating.
The lungs on the other hand are different. EACH breath is DIRECTLY controlled by the brain steam giving a steady signal: Breathe, Breathe, Breathe, etc. In the absence of the brain steam (or if the nerve that conducts this signal is damaged) the patient will stop breathing.
Again: His heart will still keep beating (assuming you provide a steady supply of oxygen obviously) becasue the heart’s signal to Beat, Beat, Beat…. does NOT come from the brain, it comes from the heart itself
“Assuming I didn’t, my point was that zero function of brain stem reflexes by itself could never be an actual way to determine death,”
Again, I’m not sure what you mean by “never be an actual way to determine death,” do you mean halachaicly? Most poskim do say that (for varied reasons), however some disagree. If you mean legally ALL states disagree with you.
“because if the major (heart or lungs) organs are working, that is proof of some brain activity.”
Again, no the heart can (and has) functioned completely perfectly in the absence of a brain.
“The possibility of having life without the major organs is zero, even with a functioning brain stem.”
I’m nost sure what you mean with this sentence. Patients are put on Heart bypasss machines daily for surgery etc. I believe all would consider them alive even though for a period their “major organs:” werent functioning (after R” Yechezkal Roth underwent cardiac surgery there was a rumpr that he was mekadesh his wife again but even if true, this is far from the standard view)
“Since the patient is not breathing, the only question is how to view the mechanical heart.”
Correcct.
“That is not a question of brain function, as the brain can function (albeit in a meaningless manner) without the heart or lungs.”
I’m not sure what you mean by “meaningless manner” I would think its very meaningfull that a person with an artificial heart and who is ventilated still has his own brain function. In fact according to those who reject brain death, I’m not clear on what basis he is alive There is also the problem of the sheep experiment.
Though IIf I understand your point correctly, I believe R’ Dovid Feinstein made this point when explaining his father’s postition According to R’ Moshe: The brain, in of itself, has no bearing on whether a person is alive or not. If he is breathing independently he is alive, if not not. (note: If a vent is helping him breathe he’d still be alive, if the vent is completely breathing for him then he isn’t) A brain dead patient BY DEFINITION is not breathing on his own your last statment is correct ” If there is medical brain death without apnea, than I am completely wrong.” There is no brain death without apnea, by defintiion. thus according to his teshuvos and family, R’ Moshe held a brain dead person is dead (becasue he isnt breathing not becasue of lack of brain activity per se)