The Scottish philosopher and historian David Hume (1711-1776) believed that when thinking about politics we should assume that every man and every institution pursues their own self-interest often at the expense of the public good:>
Political writers have established it as a maxim, that, in contriving any system of government, and fixing the several checks and controuls of the constitution, every man ought to be supposed a knave, and to have no other end, in all his actions, than private interest. By this interest we must govern him, and, by means of it, make him, notwithstanding his insatiable avarice and ambition, co-operate to public good. Without this, say they, we shall in vain boast of the advantages of any constitution, and shall find, in the end, that we have no security for our liberties or possessions, except the good-will of our rulers; that is, we shall have no security at all.
ESSAY VI. OF THE INDEPENDENCY OF PARLIAMENT
Political writers have established it as a maxim, that, in contriving any system of government, and fixing the several checks and controuls of the constitution, every man ought to be supposed a knave, and to have no other end, in all his actions, than private interest. By this interest we must govern him, and, by means of it, make him, notwithstanding his insatiable avarice and ambition, co-operate to public good. Without this, say they, we shall in vain boast of the advantages of any constitution, and shall find, in the end, that we have no security for our liberties or possessions, except the good-will of our rulers; that is, we shall have no security at all.
It is, therefore, a just political maxim, that every man must be supposed a knave: Though at the same time, it appears somewhat strange, that a maxim should be true in politics, which is false in fact. But to satisfy us on this head, we may consider, that men are generally more honest in their private than in their public capacity, and will go greater lengths to serve a party, than when their own private interest is alone concerned. Honour is a great check upon mankind: But where a considerable body of men act together, this check is, in a great measure, removed; since a man is sure to be approved of by his own party, for what promotes the common interest; and he soon learns to despise the clamours of adversaries. To which we may add, that every court or senate is determined by the greater number of voices; so that, if self-interest influences only the majority, (as it will always do) the whole senate follows the allurements of this separate interest, and acts as if it contained not one member, who had any regard to public interest and liberty.
When there offers, therefore, to our censure and examination, any plan of government, real or imaginary, where the power is distributed among several courts, and several orders of men, we should always consider the separate interest of each court, and each order; and, if we find that, by the skilful division of power, this interest must necessarily, in its operation, concur with public, we may pronounce that government to be wise and happy. If, on the contrary, separate interest be not checked, and be not directed to the public, we ought to look for nothing but faction, disorder, and tyranny from such a government. In this opinion I am justified by experience, as well as by the authority of all philosophers and politicians, both antient and modern.
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