The message that I think is key here is not the one Tim focuses on. His message is "I think you're special, but, you fall within a bell curve". That's not the important message, the important line is "the connection is strengthened, the affection simply grows over time". That's the point of love. You know when you find THE ONE when you're in secondary school, and your parents say it's just puppy love? Nonsense. Of course you can find your One True Love in secondary school, I did, three times.
I can name off the top of my head 5 people I would give anything to spend the rest of my life with. The odds are I will spend the rest of my life with none of them, but that doesn't stop all of them from being That One Special Someone. Because despite the name we all have special someones, lots of them. What makes the One Special Someone you end up with special is exactly what makes all the others special. You're no more inherently destined to one than any other, it's only the perspective at the end that makes it seem like this. It's easy to see it as inevitable that life would evolve towards humans because here we are, but slime moulds are just as special, they're here just the same, no reason your great^n grandfather couldn't have gone left not right when the split was happening.
And exactly the same is true of life. I am a strong advocate of abortion, and get into debates on the topic. The problem most people I talk to have is that the foetus would have turned into someone special, and yes, it's true. You name any person you love and imagine life in a world where they had never existed. It's terrible, the world feels empty. Except that that's not how love works, you're no more destined to love that friend as you are destined to be with that particular The One. Who they are because of genetics or environment means nothing. All, and I mean all, that matters morally about a person is love. And not in some bull "love is all around us" hippie sense. As in it is only by loving someone that they mean anything to us. And what people mean to us is all that matters in the abortion debate. Lets not pretend we care about a foetus for its own sake, not when we slaughter cattle far more intelligent and important by the million. What matters is what that foetus means to us, the fact that it's a cute little baby, or that it's going to grow up to be the son we love.
When you think of abortion you think of two things, one, a cute baby, two, the grown person who you love. The first is purely an emotive hook, a foetus is not as cute as a baby, and certainly not as cute as the animals that people eat every day. The second is to think, if this baby grows up it can be my daughter who I'd love, we'd go dancing and she'd be wonderful. I would hate if someone took my daughter away, so I must hate just as much someone taking this thing that will become her away. The error as I see it is in thinking about things as they will become and assuming the properties are there in the starting materials. It's the same remnant of vitalism that stops stem cell research. There is no gene for "being the apple of dad's eye". Nothing about an egg cell is loved. Love grows over time. What matters to us, what makes a person special is memories, emotions, love.
If I had never met whoever turns out to be the person I will spend the rest of my life with I would not notice. If I never have the son that makes my life worth while it would matter just as little. Because "making life worth while" is not a property that an foetus can ever have. "Making life worth while" is a property of a person, of memories with that person, of long hours in someone's arms, of days in front of the TV, of special times. It's a sin to destroy the mona lisa, it's not a sin to destroy paint, what you do with it is what matters, not what things are. As always, Carl Sagan puts it beautifully:
The beauty of a living thing is not the atoms that go into it. but the way those atoms are put together.
And with a person, with someone we love, they're put together by our actions as much as nature.
This is why when I'm old and infirm, or ill and incurable or in pain and without relief I shall kill myself. Because bodies dont matter, what matters is memories and experiences. There are two questions to ask before you can do something like this, first, is it right for me, and I have no interest in existing if that means being in pain or incontinent or unable to prove Pythagoras' theorem. The second is, is it fair on those around you. It's selfish to deprive someone of somebody who is special to them, or who they love. However, I have no such worries. Being in this body isn't what matters to any of you, what matters to all of you is your experience of me. The times we've spoken, and hugged, and argued, and sat around doing nothing. If I want to end my life I wont worry that something has gone, even if only to "the next great adventure". Because I'm soul-less, literally, that's what it means to be an atheist, you give up your concept of a soul, say that there is no vital essence of me-ness. So when I die, you will be deprived of nothing except what I would have done with you in the future, and if I dont want those times I doubt they'd be that interesting for you either.
Love is a part of how we see the world, but it's not a magnetic attraction of souls, there's no such thing. It's about memories, our memories of a person are why we love them, and why we cant miss a person we have no memory of. Some years from now I will be sat with that One Perfect Someone and I will think about how special they are, and how far from special everyone else I've ever known is. I just hope I can remember that it's not because of anything trivial or boring like souls. It's because of what that person has done with me (not like that (well yes like that, but not just like that (way to ruin the mood))), it's because of work, of memories. That person wasn't just born special so we could slot into eachother(watch it)'s lives so perfectly. It was because we made an effort, because of all the little things, because they were there for me, and I for them. I have only one life, and if you dont put the effort in there's no point in it.