I don’t believe the following three arguments are definitive, but I think they are interesting. I have taken them–or the roots of them–from an article on the topic by D.W. Haslett (“Is Inheritance Justified,” PAPA, Vol 15 #2, 1986: 122-155; I don’t know if Haslett would approve of my formulations).
I believe that adults should be, or should strive to be, self-sufficient and that parents are morally obligated to seek to raise their children in a way that makes it likely that they will, as adults, be self-sufficient. I don’t want, though, to discuss those claims here. I will note that by “self-sufficient,” I do not mean living in such a way that one never depends on or cares for any other. Perhaps some are capable of living a good life without doing so, but most of us fare better having loved ones. Nor do I mean, of course, that one should seek to never trade with others. Trading with others obviously helps most of us live well. What I mean, then, is taking care of oneself, given the way one finds oneself in the world, with the participation of others that one voluntarily engages with with who are not themselves morally or legally required to do as they do. (That last is vaguer than I would like, but will have to do.)
If government provides one the resources to live one’s life, one is not self-sufficient (taxpayers are legally required to provide the aid). So too, if one’s parents (or other family members) provide one the resources to live one’s life, one is not self-sufficient (presumably they are–or feel–morally bound to do so). It may be the case that with family, but not with government, there is no force involved. That is not to the point here. One is not taking care of oneself if one’s parents are. When we are young, of course, our parents should take care of us; when we are adults, this is no longer the case. If this is right, adults should not receive inheritances. At least absent other considerations.
The previous paragraph was a simple (perhaps too-simple) argument from self-sufficiency to absence of inheritance (for adults). What follows is an argument from equal opportunity and an argument from productivity to absence of inheritance (again, for adults).
First the argument from equal opportunity. I think equal opportunity is, in itself, valuable. I think this for the simple reason that I do not think one enters the world deserving unequal opportunities. Bill Gates’ children are lucky that they were born to someone able to provide them many opportunities. Many people are unlucky because born to parents who cannot. The former no more deserve opportunities than the latter. Of course, they have far more opportunities–because they inherit wealth from their parents. Inheritance is clearly opposed to equal opportunity, so if you value the latter, you should (to the same extent) dis-value the former. But even if one does not think equal opportunity is valuable in itself, its instrumental value is important.
So, now the argument from productivity. More wealth is produced in a society when there are more people to come up with new ideas of things to produce and new ideas of how to produce things already being produced. Innovation drives wealth-creation. Whoever invented the mp3 made carrying music far easier and less expensive–thus allowing for wealth creation. When Henry Ford designed the assembly line, making production of cars quicker and less expensive, he made possible much wealth. People are more likely to innovate–both with new things and new ways to produce things already produced–when they have opportunities to be educated, to travel, to experience a variety of things, etc. When people live in poverty, they lack opportunities. If we could alleviate the poverty we would increase their opportunities and, all else equal, the innovations they could bring to market–and thus the wealth in society. It would seem that removing inheritance–which, I grant, gives many opportunities to those who are lucky enough to receive them–would allow a greater (wider) distribution of resources, thereby increasing the opportunities for all (and arguably, the freedom). Of course, this is contingent on (a) it being true that lack of inheritance means greater distribution and (b) the decreased incentives to produce (of those who would otherwise be able to bequeath inheritances) not being too significant or being offset by other considerations (like the increased productivity of those with opportunities they would not otherwise have). I suspect (a) and (b) are both possible, so I suspect we can increase the average number of opportunities available for all by removing the possibility of inheritance. Doing so, as I indicate above, would increase the innovations and thus wealth in society, so would be good. (I grant, by the way, that wealth is not the only factor involved in individual welfare. It is nonetheless clear that wealth contributes to welfare.)
As I said, I am not sure these arguments are definitive. If the system they support genuinely involves violating individual’s rights, for example, that would matter. I am not sure it would do so, though, as in a society where no one expected to be able to bequeath or receive inheritances, its unlikely that anyone would think there was a right to do so–and, arguably, unlikely that there would be such a right. (This sort of thinking fits, I think, with Michael Otsuka’s left-libertarianism.)