Unproductive labourers, and those who do not labour at all, are all maintained by revenue; either, first, by that part of the annual produce which is originally destined for constituting a revenue to some particular persons, either as the rent of land, or as the profits of stock; or, secondly, by that part which, though originally destined for replacing a capital, and for maintaining productive labourers only, yet when it comes into their hands, whatever part of it is over and above their necessary subsistence, may be employed in maintaining indifferently either productive or unproductive hands.