No tax regime, whether flat-tax, progressive, VAT, …. is value-neutral. Although certain believers in markets might consider “the least invasive” tax policy, or “the most market-neutral” tax policy to be value-neutral, it is still in fact social engineering. That’s a four-letter word so people shy away from it. But as economists have argued when discussing the value of a human life, “doing nothing” is doing something. Just so, letting “the market” mete out $ is just as much a social-justice programme as wealth-redistribution.

There is a (small) strand of research looking at the philosophy, ethics and normative aspects of behavioural economics – some of Bob Sugden’s work for example is in this area. But there is definitely a niche waiting to be filled here. When we build a sufficiently detailed descriptive model of how psychological factors lead to apparent preferences, and then to choices, there is the possibility that normative questions get squeezed out. I am not sure exactly at what level to reintroduce them, but it is worth exploring.