Thanks for the comments. Yes. Lots of things may well evoke sympathy and empathy--heartbeats for example--and we shouldnt throw these aside without considering them.
So--lets consider them. A person can be fully brain-dead and have a heart beat. Life is not one single thing--its a bunch of processes--mostly metabolic processes. We like to summarise it as "life" but this is a a hang-over of humans thinking in essentialist terms. Nature isnt about essentials--its about functions and a heartbeat is just one of many. It is not even a particularly myserious one (unlike a lot of puzzling brain functions, for example) and we could create a completely artificial heartbeat. A critter with an artificial heart wouldn't suddenly become a baby, or something of moral weight, just because we had put a sophisticated pump in it. So--the "heartbeat" thing feels like emotional manipulation, rather than an honest drawing of attention to morally salient features of an individual.

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