For instance, we know nuclear bombs are bad for people's health. But we don't know precisely HOW bad. We can't say precisely how many people would die from a nuclear war. But whether it's 3 million or 3 billion is an academic question. The same is true for the big numbers of people who die from starvation and preventable disease.
Nobody seriously contests that millions are dying of starvation.
The fact is, we haven't done enough in either case. As long as we haven't exhausted all our means to help that first million, it's not useful to argue over whether we've finished the work, or whether there's another 16 million waiting for help. We know that there are enough resources to insure a healthy life for everyone on the planet. We need to start distributing them. So we should talk about HOW to distribute them.