But no modern treatise on political science, whether dealing with institutions or finance, now begins with anything corresponding to the opening words of Bentham's _Principles of Morals and Legislation_--'Nature has placed mankind under the governance of two sovereign masters, pain and pleasure'; or to the 'first general proposition' of Nassau Senior's _Political Economy,_ 'Every man desires to obtain additional wealth with as little sacrifice as possible.'[1] In most cases one cannot even discover whether the writer is conscious of possessing any conception of human nature at all.
[1] _Political, Economy_ (in the _Encyclopedia Metropolitana_), 2nd edition (1850), p.

26.
It is easy to understand how this has come about.

Political science is just beginning to regain some measure of authority after the acknowledged failure of its confident professions during the first half of the nineteenth century.

Bentham's Utilitarianism, after superseding both Natural Right and the blind tradition of the lawyers, and serving as the basis of innumerable legal and constitutional reforms throughout Europe, was killed by the unanswerable refusal of the plain man to believe that ideas of pleasure and pain are the only sources of human motive.

The 'classical' political economy of the universities and the newspapers, the political economy of MacCulloch and Senior and Archbishop Whately, was even more unfortunate in its attempt to deduce a whole industrial polity from a 'few simple principles' of human nature.
It became identified with the shallow dogmatism by which well-to-do people in the first half of Queen Victoria's reign tried to convince working men that any change in the distribution of the good things of life was 'scientifically impossible.' Marx and Buskin and Carlyle were masters of sarcasm, and the process is not yet forgotten by which they slowly compelled even the newspapers to abandon the 'laws of political economy' which from 1815 to 1870 stood, like gigantic stuffed policemen, on guard over rent and profits.
When the struggle against 'Political Economy' was at its height, Darwin's _Origin of Species_ revealed a universe in which the 'few simple principles' seemed a little absurd, and nothing has hitherto taken their place.