If you are reading this blog whilst having sexual intercourse with the intention to conceive a child, then I admire your skill at multi-tasking. But it's pretty safe to assume that you aren't doing so. Most, if not all of us, spend most of our lives abstaining from procreation. We could produce a multitude of children (touch wood (no pun intended)), but we choose not to, and that choice seems perfectly reasonable. In fact, the contrary would be absurd.
And yet according to the very sensible moral theory of Utilitarianism, we have a duty not only to minimise pain (or unhappiness), but also to maximise pleasure (or happiness). Therein consists morality, according to the utilitarian. But if we have the ability to bring people who'll presumably live happy lives into existence, and the duty to maximise happiness, it seems that we straight forwardly have a duty to bring people into existence. And the best way to do that is by engaging in sexual intercourse. (Everything up to this point is my standard pick-up line). So how do we sleep at night knowing that we should be awake, busily procreating?
One popular answer to this 'Problem of Procreation' is to bring in what I'll call 'The Principle of Non-Existence', and suggest that our potential children, insofar as they don't yet exist, shouldn't be considered as agents to which we have duties. The Principle of Non-Existence says that we don't have duties towards beings which don't yet exist, or that the potential pains and pleasures of beings that don't yet exist don't matter. That seems reasonable: it's not as if our billions of potential children are sitting around in some cosmic waiting-room and being shot each time we decide not to engage in 'business time'.
And yet the Principle of Non-Existence doesn't hold water. Devastating the future of the natural environment and therefore denying the basic needs of future humans simply to maintain our luxurious lifestyles seems unambiguously wrong (though often inconvenient enough to ignore) and yet those who would suffer the effects of our irresponsibility don't yet exist. Furthermore, artificially creating billions of organisms which will suffer immense pain for a year and then die would be a villainy of science-fiction proportions, despite the non-existence of the potential victims at the time of choosing whether or not to create them.
On the contrary, all that seems to matter is that the victims of the above horrors will exist, even if they don't now. And that won't help us with the Problem of Procreation, since our future happy children would exist too, if we chose to allow them. What does seem to be a relevant difference between the dystopian outcomes above and the possibility of our children existing is that the former involves suffering, whereas the latter, unless we're really awful parents, involves (a net 'amount' of) happiness. Here is where the difference lies.
I want to claim (and this will require a more thorough treatment elsewhere) that, contrary to classical utilitarianism, our moral obligation is not to maximise pleasure (or happiness), but merely to minimise pain (or unhappiness). This explains why we have an obligation not to bring tortured beings into existence, but why we don't have an obligation to produce children (whose lives would involve a net 'amount' happiness) whenever we possibly could. Whilst bringing about happiness is a bloody nice thing to do, it's an act of supererogation, i.e., going beyond the call of duty. We never have a duty to bring about happiness, per se, but only a duty to prevent or stop pain and suffering.
Of course, sometimes the lack of a pleasure can itself be a pain. We aren't indifferent with regard to lost pleasures: missing out on something that would make us happy and losing something that did make us happy are not merely lost pleasures, but are themselves pains. This deals with an obvious objection to my overall claim, for it might be said that since we don't have a duty to bring about pleasure, we have no duty to abstain from acting 'spitefully', say, by altering our unborn child's genetics so that they are infertile, or making a fat kid an empty promise of cake. These actions are (in varying degrees) immoral, but they're immoral because the frustration of a desire is itself often a pain, rather than because the frustration of a desire or the denial of a pleasure are inherently wrong.
The claim that we only have a duty to prevent or stop pain has much greater applications than the Problem of Procreation, but I think that the problem is the best example of the kind of error we get into when we think that we have an obligation to produce pleasure. By denying the duty to produce pleasure we've managed to avoid the obligation to continuously attempt procreation without having to accept the principle of non-existence and the unwanted conclusions that come with it.
Now let it never be said that philosophy does anything to cause or increase the likelihood of sexual intercourse.