Traditional utilitarianism: Benthamism
For hedonism, pleasure is the only summum bonum - the fundamental motive of human conduct. Pleasure is an emotional index of a situation favourable to the conservation of human species. According to Bentham (1948 , p. 125), pleasure (and pain) governs us, and are the foundation of human life and legislation; while things such as freedom, truth, justice and nature are only means to reach the greatest pleasure.
Hedonism, intended as 'egoism', claims that pleasure for one person is good for that person only; while intended as 'utilitarianism', it claims that the general pleasure is good for a community. In particular, utilitarianism in Bentham's version (1948 , pp. 126-7) claims that
the community is a fictitious body composed of the individual
persons who are considered as constituting as it were its members.
The interest of the community then is, what? - the sum of the interests of the several members who compose it. ... A thing is said to promote the interest, or to be for the interest, of an individual, when it tends to add to the sum total of his pleasures: or, what comes to the same things, to diminish the sum total of his pains.
The atomism hypothesis (methodological individualism in human sciences) and an aggregative conception of interpersonal impartiality (agent neutrality) are at the basis of Benthamism. According to atomism, society is a collection of independent parts, and not an organic whole. It is a stable structure, governed by material laws, not by psychological laws; thus, agents act with the regularity of heavenly bodies. The hypothesis of interpersonal impartiality, meanwhile, means that it is not rational to prefer the happiness of one person to that of another, so that the moral importance is attributed to pleasure alone, and not to whoever has pleasure (Brink, 1993).
Since the sole rational object of conduct is the greatest pleasure of the greatest number, Benthamism claims that the value of the consequences of any action is exactly measurable, and morality aims to maximize utility,1 intended as the exact balance between pleasure and pain with respect to the total number of individuals in a community. Interpersonal comparisons are admitted without any discussion, and each agent is assigned the same weight. Bentham evaluated everything in money terms, and in doing this he was inspired by Cesare Beccaria. According to Bentham (Venturi, 1965, p. 563), Beccaria was the first to introduce into the field of morals 'the precision, the clarity and the incontestability of mathematical calculus'. Beccaria (1965 , p. 20) specifies that, in political arithmetic, mathematical exactitude has to be substituted by the calculus of probability. Therefore, when the tendency of any action is estimated, not only are pleasures and pains numerically measurable and arithmetically additive, but probabilities, too, are numerically measurable and comparable.
Since private interest and social good have to be in harmony, Bentham's fundamental problem is to justify the belief that individual hedonism when it is rationally enlightened is utilitarian hedonism. Stark (1941, pp. 68-73) maintains that this belief is grounded in the assumption of 'human equality'. In particular, as regards economic situations, Bentham follows the principle of the natural identity of interests, which means that 'the various egoisms harmonise of their own accord and automatically bring about the good of the [human] species',2 through free exchange and the division of labour. In other terms, Bentham's society is seen as a collection of homogeneous agents who regularly behave in a social environment in which laissez-faire is admitted. Each equally egoistic agent is equally able and free to behave according to reason, that is, to compare pleasures and pains. This gives a scientific foundation to the belief that private interest and social good are in harmony. Therefore, as Keynes (1972b , p. 275) claims, 'the political philosopher could retire in favour of the business man - for the latter could attain the philosopher's summum bonum by just pursuing his own private profit'. This view considers economics as a moral science, where the main task of policymakers is to promote social utility through punishments and rewards.