The authors’ major contention, that if it is okay to give something away for free, or to accept something from another person without payment, then it is in principle okay to have a market in that something. I think this is a major contribution to the debate over commodification, mainly because it leads us to avoid quarreling about a lot of irrelevant issues. For instance, you cannot sell your child as a sex object, or to be sacrificed for organ transplant material because you don’t have the right to give away your child for these purposes. Similarly, it is beside the point that current markets are not properly regulated (e.g., for sexual services) because than can in principle be well regulated in the public interest.
The authors contend that this principle is universal, but they may be significant qualifications. For instance, some things that are permissible may nevertheless be socially undesirable, especially if they become common. If markets in such a thing are suppressed the level of the activity might be quite low, but when markets are opened in this thing, the level might grow to very harmful levels.
At any rate, the book is a pleasure to read and very though-provoking. I predict it will lead to a much higher level of debate about commodification in coming years.