Taxes upon possessions are levied without expense, but have every other disadvantage. Most states, however, are obliged to have recourse to them, in order to supply the deficiencies of the other. But the most pernicious of all taxes are those which are arbitrary. They are commonly converted by their management into punishments on industry; and also by their unavoidable inequality are more grievous than by the real burden which they impose. It is surprising, therefore, to see them have place among any civilized people. In general, all poll-taxes, even when not arbitrary—which they commonly are—may be esteemed dangerous; because it is so easy for the sovereign to add a little more and a little more to the sum demanded, that these taxes are apt to become altogether oppressive and intolerable. On the other hand, a duty upon commodities checks itself, and a prince will soon find that an increase of the impost is no increase of his revenue. It is not easy, therefore, for a people to be altogether ruined by such taxes. Historians inform us that one of the chief causes of the destruction of the Roman state was the alteration which Constantine introduced into the finances, by substituting a universal poll-tax in lieu of almost all the tithes, customs, and excises which formerly composed the revenue of the empire. The people in all the provinces were so grinded and oppressed by the publicans that they were glad to take refuge under the conquering arms of the barbarians, whose dominion, as they had fewer necessities and less art, was found preferable to the refined tyranny of the Romans.