If every man always pursues his own pleasure, how are we to secure that the legislator shall pursue the pleasure of mankind in general?
 Bertrand Russell, A History of Western Philosophy (1945). copy citation

Context

“His main positive argument in favour of his principle is that it is really implied by apparently different ethical systems. This, however, is only made plausible by a severe restriction of his survey. There is an obvious lacuna in Bentham’s system. If every man always pursues his own pleasure, how are we to secure that the legislator shall pursue the pleasure of mankind in general? Bentham’s own instinctive benevolence (which his psychological theories prevented him from noticing) concealed the problem from him. If he had been employed to draw up a code of laws for some country, he would have framed his proposals in what he conceived to be the public interest, not so as to further his own interests or” source