OK, I see. I tried again to parse it. It's awkward wording, but the "this" has to refer to "helping other people", as the previous sentence is "We should help

OK, I see. I tried again to parse it. It's awkward wording, but the "this" has to refer to "helping other people", as the previous sentence is "We should help other people." So then it means "We should strongly consider how much effort we devote to helping other people". Paraphrased, I interpret that to mean, "We should ask ourselves whether we do enough to help other people". Only in the next sentence do we get to "Some methods of helping people are more effective than others." Only after that in the chain of logic could come the idea "we should put a lot of thought into figuring out which methods are more/most effective". I'd say that the latter idea is presented as being in the next level of the tower, stated as "Utilitarian calculus (eg QALYs)".