Act-utilitarianism states that we should always perform
Harsanyi’s first claim is that a society of act-utilitarians is unable to produce optimal outcomes through coordination, whereas a society of rule-utilitarians can. Harsanyi (1908) asks us to imagine two possible worlds: an act-utilitarian world in which it is common knowledge that everyone is an act-utilitarian, and a rule-utilitarian world in which it is common knowledge that everyone is a rule-utilitarian. Common knowledge [that X] means that everyone knows that X, everyone knows everyone else knows that X, etc. In other words, each utilitarian agent has to regard the other utilitarian agent’s strategies as given.
Consider the following scenario (Harsanyi 1908): 1000 voters have to decide the fate of an important policy, which needs 800 affirmative votes. They all support the policy, but going to vote will incur minor costs. Communication is forbidden, and they cannot find out whether others have voted or will vote. In the act-utilitarian world, a voter will vote only when she is fairly sure that
However, the voting scenario’s setup seems unfair to act-utilitarianism. Since everyone knows everyone is a rule-utilitarian in a rule-utilitarian world, every agent will definitely choose to follow the rule that “everyone vote”, which creates a far better outcome. This seems to assume a rather high level of common knowledge, which favours rule-utiltarianism. But in reality, such common knowledge is very difficult to achieve. On the other hand, the voters are deprived of the knowledge of other’s voting behavior. In reality, however, there is usually good evidence whether the vote is going to be tight or not. If act-utilitarians have access to this knowledge, it will be much more likely to result in a good outcome. Also, in Harsanyi’s act-utilitarian world, agents will only vote when
Harsanyi’s second claim is that many important things will be lost in a society of act-utilitarians, and hence, it fails to maximize the total sum of wellbeing. People will break a promise or take other’s property whenever it promotes the social good. Without trust, the society will lose the benefit of the practice of promising, such as the ability to form reasonable expectations about other’s future behavior (which will create a sense of security and make it easier for us to plan for our future), and the opportunity to increase social good through coordination. Without property right, our incentives to engage in socially desirable activity will be greatly reduced. Moreover, special duty—including parent-children relationship—does not have a place in a society of act-utilitarians. However, such relationships have strong informational and motivational advantage, allowing the agents to be aware of other’s special need and develop emotional tie. On the other hand, rule-utilitarianism is able to acknowledge these beneficial effects by suggesting that they correspond to rules such that if everyone follows them, sum of wellbeing will be maximized. In other words, we should generally keep promises, respect property right, and look after our own children according to rule-utilitarianism. Again, rule-utilitarianism performs better in utilitarian terms.
However, Harsanyi is erroneous in assuming that act-utilitarians only follow a simple and naïve model of decision-making. As a matter of fact, sophisticated act-utilitarians can actually take the aforementioned benefits into account. In a world of sophisticated act-utilitarians, the agent will not easily break a promise because they realize that their interactions with others are often
My last worry for Harsanyi is that both of his arguments involve the following inference: it is good that everyone is committed to rule-utilitarianism; therefore rule-utilitarianism is correct, and we should act in accordance to rule-utilitarianism. But this is controversial. Imagine a billionaire will pay you one million dollar—all you have to do is to
To conclude, Harsanyi’s comparison between act-utilitarianism and rule-utilitarianism is unfair. His argument also involves a doubtful inference.
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Harsanyi, J. ‘Rule utilitarianism, rights, obligations and the theory of rational behaior.’