In his Lectures on Jurisprudence (1763) Adam Smith discusses the "very figurative metaphoricall consent" that people are supposed to grant the ruler to tax them. When taxes become "very exorbitant" he believes the people have the right to resist as the Americans did in 1775:
It is in Britain alone that any consent of the people is required, and God knows it is but a very figurative metaphoricall consent which is given here. And in Scotland still more than in England, as but very few have a vote for a Member of Parliament | who give this metaphoricall consent; and yet this is not any where reckoned a sufficient cause of rebellion. No doubt the raising of a very exorbitant tax, as the raising as much in peace as in war, or the half or even the fifth of the wealth of the nation, would, as well as any other gross abuse of power, justify resistance in the people.
About this Quotation:
In these lectures on jurisprudence, given in 1763, Adam Smith makes a number of claims which have great significance for the coming American Revolution and for political theory in general. In a discussion of “exorbitant taxation” (which Smith seems to believe is somewhere between 1/5 and ½ of a nation’s wealth) he mentions the consent theory of John Locke, in particular the idea of “implied consent”. This is the notion that by not revolting the government can “imply” that “consent” to its legislation has been granted by the citizenry. In the case of taxation in Britain, Smith mocks this idea by calling it sarcastically “very figurative metaphoricall consent”, i.e. no consent at all. When taxes do rise to these shockingly high levels (1/5!) the people have the right to resist their government, as the Americans were shortly to do.