To claim a share of such wealth without being willing to make this contribution is unfairly to free-ride on those citizens who do make the required contribution. If this unfairness is to be avoided, receipt of an equal share of the relevant types of external wealth must be made conditional on a demonstrated willingness to make the required contribution. And it is therefore inappropriate to redistribute such wealth in the form of an UBI precisely because doing so would disconnect enjoyment of this wealth from making the relevant contribution, and would thus permit free-riding. This is, of course, the exploitation objection to UBI. (source)