At the moment of conception, the microscopic life that will become a bawling infant is only 2 cells. You cannot see it with the naked eye.
The two people who made this little zygote are composed of about 15 to 70 trillion cells each. That's trillions.
The difference between 2 cells and 40 trillion cells is fairly significant.
When does life begin?
The first choice is at the moment of conception.
The second choice is at some arbitrary point in time and development after that moment of conception.
The first choice is clean. It doesn't involve any judgment in terms of starting point. It is simple.
It is also absurd because it suggests that two microscopic cells deserve legal rights. Surprisingly, the folks protesting abortion are supporting a life that they can't see and that can't see them. Unsurprisingly, the folks who protest abortion tend to have religious objections; it is this group that is used to advocating on behalf of the unseen.But if you're going to protect life from the moment of conception, why not make contraception illegal? Why not protect the sanctity of "human" life at the instant before conception as well as the moment after?
The second choice is reasonable. It acknowledges the silliness of arguing that two microscopic cells are human in the same way that a baby in a high chair is human.
It is also just as bad. It involves all sorts of judgments about a starting point. At what point might this life be viable? When might a mother first realize that she's pregnant? When is the fetus conscious? Conscious by what standard? Are you just going to pick some day at random out of this string of 266 days? Why day 112 but not 113? Or day 199 instead of 200? This is unconscionably murky about the starting point for something as important as life. Get it wrong by even a day and we are killing human beings rather than terminating a pregnancy.
I find the notion that life begins at conception emotionally appealing. It is clean. It's almost romantic, certainly spiritual to imagine "life" begins in an instant, an instant when it is scarcely corporeal.
I also think that it is more rational to acknowledge that "life" at the moment of conception is not really different from the "life" of living egg and sperm cells. There is nothing human about sperm or eggs except for the DNA, DNA that can be found in skin cells or saliva. Again, you can't even see it. It makes more sense to refrain from equating mere cells with a human being until some development threshold has been reached.
It is a choice between the heart and head, the romantic or rational.
So what to believe? Whatever you'd like. At least with current laws.
The beauty of current laws is that a person can go with the rational decision that "life" is something we'll never precisely time and the visceral decision that "life" is something that transcends our normal powers of perception. We're not forced to live by someone else's indefensible standards. And this is fitting because the only thing more absurd than having to defend either of these choices is having one of them forced on you.