The response to my previous post regarding abortion has been very interesting, and led to a great deal of thought. As is usual with this issue, a lot of time has been spent discussing when an egg can be considered as "potential life". I'm by no means suggesting this isn't a worthwhile consideration, but I did want to make the follow-up point that uncertainty about a situation does not prevent the existence of moral choices regarding that situation.
I figured a bit of a thought experiment might be illuminating here. Consider the following situation. Four people are led into different rooms, each one containing a sealed box (no person sees any other, or is even aware they are involved in the experiment). Each is told that by pressing a button on the box they will receive a million pounds.
Person 1 is told there is a man inside the box, and that pushing the button will fill the box with deadly gas.
Person 2 is told there might be a man inside the box, and that pushing the button will fill the box with deadly gas.
Person 3 is told there might be a man inside the box, and that pushing the button will fill the box with deadly gas. However, there is a 75% chance the gas will be released even if they don't press the button.
Person 4 is told nothing further.
There are obviously a number of objections to be made over the specifics here. A million pounds isn't equivalent to avoiding pregnancy, I am implicitly dealing in terms of murder and death rather than the negation of potential life, and so on and so forth (of course, you could always alter the example to, say, winning £100 at the risk of breaking a man's legs). But the thought experiment is this: Does person 2 has a difficult choice to make. I would argue that they do. It is arguably made easier by not being certain that there is a person in the box or not, but it still not an easy choice.
Second, is it a difficult choice for person 3? Once again, I would argue yes. The fact that a seriously negative outcome may occur even without their input does not negate the moral responsibility of choosing to enter that input.
Finally, should person 4 be told after pushing the button that there was a man inside the box, and that they have killed them, would their response be entirely consistent with that of any previous person? In this case, my answer would be no. Certainly, we would expect them to feel guilty over what they have done. It should be fairly obvious, however, that the reaction of person 4 will be very different to that of persons 1 to 3. The end result is only part of a human response, the level of knowledge is also a significant factor.
The only point I am trying to make here is that it is most certainly not the case that lack of certainty about a situation implies there can be no moral cost to an action (thus those of us who support abortion rights must find alternative justifications), and that it does not follow from a lack of certainty that there should be no difficulty in making the relevant decision.
(As a side note, you could have a fifth person who is told there is a man inside the box, and that pressing the button might release deadly gas. It would be interesting to see how different their response would be to that of person 2).
Edited for clarity.