Determinism.....

[Violet]

I suppose the value of the life of both are still the same, though of course it does throw a spanner in the works.

Well you can only really go by what you know, and if you dont know whos in the train you can only go by the lesser of two evils.

It's always one's own choice to make... given whatever the situation.

Yeah because they are unjust, but they are unjust because certain things are wrong and certain things are right (ie: an absolute moral law).

No, they are unjust because they are unfair. Fairness is when one receives what they deserve... unfairness is when they receive more or less than they deserve. Of course, what one deserves is subjective, just like morals... but they are not essentially related. Eg: Say that murdering people is immoral... but a war medal is what your hero deserves for committing this immoral act.

Given that, what would you think about a Christian killing an abortion doctor if the person's reasoning was along the same line?

Because it is ridiculous to think that you can kill that which has never been born? The person's logic would be faulty in this case... for not only does abortion help 'save?' the life of the would-be mother: it keeps children from being raised in a negative circumstance by people who are not prepared to have them... and finally it is ridiculous to think that you can kill that which has never been born. Prevent birth from occurring ≠ murder unless the mother had intended to have the child (placing worth on the child, much like christians place worth on 'God').

Also: One of those children could have grown to be a tyrant that would kill many more people than the abortion doctor.