Here's a thought experiment due to Gregory Kavka. A couple wants to buy a new yacht for $50,000, so they agree to create a slave-child for an evil man. Once they sign the contract, the deal is irrevocable, and they know that. The child is born and the evil man takes possession. It turns out the master is reasonably enlightened. Life is not totally horrendous for the child, as he grows up. He has a life worth living, as he would insist, if asked. He doesn't wish he'd never been born. It would just be much better for him if he weren't a slave. If the slave hadn't been born a slave, he wouldn't have been born at all. (The couple may still have procreated, but at a different time, under different conditions, and the sperm-egg combination would have been different.) So why was it wrong for the couple to create this child?
The couple did lots of wrong things--they sold a child, etc. But the only thing at issue here is the creating of the child. What is wanted is a principle P that the couple violated in creating a child with such a dismal (but not rock bottom) future. This game has lots of other rules, and that's what makes it extremely tricky--
(1) P should not entail that couples must always create the best off child possible. The would imply that couples using IVF should improve embryos before implanting them, as soon as technology makes that possible. Surely that's not required; and maybe it's not even permissible.
(2) P should not entail that anyone has an obligation to have children, whether "for the sake of the child" or for the sake of others who already exist.
A curious thing about Kavka's article is that he never discusses real life slaves who (of course) had children. Were they wrong to do so? At least on first inspection, no; so we would accept a third constraint--
(3) P should entail that the couple was wrong to create a slave child, but should not condemn American slaves who had children before abolition.
So--how to explain what the couple did wrong, and also respect (1), (2), and (3)? Can it be done? I'll let you suffer with this question and look at some possible answers (including Kavka's) later in the week.