People usually take one of two perspectives when asking this question.
The first is that we should give people cash on the assumption it will be the most
cost-effective way of helping people. This view is common among economists, who think that
people are generally the best judges of what's good for them.
We agree this is a reasonable starting view, but it should be tested. In the real world,
people have imperfect information, limited motivation, and inadequate options. We need
research, here as elsewhere, to find out what works. Individuals can't always just go
out and purchase the intervention, such as psychotherapy in low- and middle-income
countries, or it might be more beneficial to them than they expect, particularly when we
account for factors like stigma. It also seems unlikely that 'just giving cash' can solve
problems which need coordination, like those addressed by advocating for lead
regulations.
The advantage of the WELLBY approach is that, through people's self-reports, we get
evidence on what actually makes a difference to their lives as they live them, not just
what they, or evaluators, expect would matter.
The second perspective is that we should give people cash even if we have good evidence
that something else would be more cost-effective. Those in this camp tend to prioritise
autonomy. As a philosophical position, we think autonomy is a contributor to happiness, but
it's people's happiness that ultimately matters: an autonomy-maximising option may not be
the best overall for someone. As it happens, our recommended charities are typically great
for autonomy too: mental health conditions are debilitating, for instance, and addressing
them empowers people.