Adam Smith is the author of An Inquiry into the Nature and Causes of the Wealth of Nations. He is known mainly as a pioneer of political economy. However, he was not only an economist but also a moral philosopher. He published The Theory of Moral Sentiments in 1759. In The Theory of Moral Sentiments, he explained an establishment of a social order based on sympathy between people in a society. Sympathy is sharing of sentiments with others by imaginarily swapping situations with others. People in The Theory of Moral Sentiments form the impartial spectator and regulate their conduct to be sympathized by the impartial spectator. The impartial spectator is often considered as an important concept in The Theory of Moral Sentiments. However, even if people formed the impartial spectator, it does not mean that they can always regulate their conduct. To regulate their conduct absolutely, people need general rules of morality. People can establish a social order thanks to general rules of morality

Some preceding studies have reinterpreted The Theory of Moral Sentiments with various research results in contemporary economics. For example, Meardon & Ortmann (1996) reinterprets self-command by using a repeated game theory model. Ashraf et al. (2005) indicates that Smith foresaw some research findings of behavioral economics. Tajima (2007) reinterprets The Theory of Moral Sentiments from a perspective of institutional economics. Bréban (2012) formularizes a behavior of people in The Theory of Moral Sentiments by using a utility function comparing with utility functions in behavioral economics. Khalil (2017) reinterprets The Theory of Moral Sentiments from a perspective of rational choice theory. These reinterpretations have shed light on modern significance of The Theory of Moral Sentiments.

However, there is room for reinterpreting important concepts in The Theory of Moral Sentiments with research results in contemporary economics. Following the preceding studies, this paper reinterprets general rules of morality and the corruption of moral sentiments by using a replicator dynamics model, which is a basic model of evolutionary economics. General rules of morality are the social norms in The Theory of Moral Sentiments concerning what is fit and proper either to be done or to be avoided. This paper interprets the corruption of moral sentiments as corruption of general rules of morality. People in The Theory of Moral Sentiments form general rules of morality through interactions with others. They continually observe conduct of others and this can lead them to form certain general rules of morality. This paper interprets this observation process as a trial and error learning process. To formularize this process, this paper uses a replicator dynamics model.

The results of the model indicate that we may interpret the corruption of moral sentiments as a transitional state. The corruption of moral sentiments is sometimes regarded as a serious problem in the moral philosophy of Smith. However, the interpretation from the results of the model can allow us to consider the corruption of moral sentiments as a trivial problem. Moreover, the results of the model clarify a meaning of sympathy in the corruption of moral sentiments. The more sympathetic players exist in a player set, the more corrupted asymptotically stable points are. This result mathematically supports an interpretation in preceding studies (Brown 1994, Griswold 1999) that sympathy can foster the corruption of moral sentiments.

The paper is organized as follows. In the section 2, we briefly describe general rules of morality and the corruption of moral sentiments in The Theory of Moral Sentiments. In the section 3, we construct a model of replicator dynamics. In the section 4, we reinterpret the corruption of moral sentiments based on the results of the model. In the last section, we conclude this paper.

People in The Theory of Moral Sentiments form the impartial spectator and regulate their conduct to be sympathized by the impartial spectator. The impartial spectator is often considered as an important concept in TMS. However, even if people formed the impartial spectator, it does not mean that they can always regulate their conduct. This is because “so partial are the views of mankind with regard to the propriety of their own conduct, both at the time of action and after it; and so difficult is it for them to view it in the light in which any indifferent spectator would consider it” (TMS. III.iv.4). Smith called this kind of problematic situation “self-deceit” (TMS. III.iv.4). According to Smith, to cope with self-deceit, Nature gave people general rules of morality. General rules of morality are the social norms in The Theory of Moral Sentiments concerning what is fit and proper either to be done or to be avoided. “General rules of conduct, when they have been fixed in our mind by habitual reflection, are of great use in correcting the misrepresentations of self-love concerning what is fit and proper to be done in our particular situation” (TMS. III.iv.12). General rules of morality are necessary to maintain social orders. “The regard to those general rules of conduct, is … the only principle by which the bulk of mankind are capable of directing their actions” (TMS. III. v.1). Smith referred to cases that people do not have to follow general rules of morality strictly. However, he hold that people should strictly follow general rules of virtue of justice, which is essential for the establishment of the social order in The Theory of Moral Sentiments. Virtue of justice requires not doing “real and positive hurt to some particular persons, from motives, which are naturally disapproved of” (TMS.II.ii.1.5). “If it [justice] is removed, the great, the immense fabric of human society… must in a moment crumble into atoms” (TMS.II.ii.3.4).

General rules of morality about actions to be avoided are formed thorough the following process. People’s sentiments are shocked from some immoral action of others, with which the impartial spectator dose not sympathize. People feel this kind of action unseemly. When people hear others express the same feeling as them, “this still further confirms, and even exasperates our [their] natural sense of their deformity” (TMS.III.4.7). For this reason, people “resolve never to be guilty of the like, nor ever, upon any account, to render ourselves in this manner the objects of universal disapprobation” (TMS.III.4.7). After repeatedly hearing others express the same feeling as them, people form a general rule of morality about an action to be avoided. General rules of morality about actions to be done are formed through a similar process as the general rules about actions to be avoided.

As we briefly explained above, general rules of morality are “formed, by finding from experience, that all actions of a certain kind, or circumstanced in a certain manner, are approved or disapproved of” (TMS.III.4.8). This process of formation of general rules can be regarded as a process of trial and error learning. Trial and error learning is a kind of empirical learning, through which people evaluate their choice based on its consequence and modify their way of choice. In the process of formation of general rules of morality, people in TMS evaluate their opinion based on whether others express the same opinion as them or not. When they know others express the same opinion as them, this justifies their opinion. People evaluate justifiability of their opinion (choice) based on whether others express the same opinion (consequence).

To formularize the learning process, this paper uses a replicator dynamics model with two strategies: virtue strategy and fortune strategy. These two strategies derive from the road to virtue and the road to fortune in the corruption of moral sentiments (TMS. I.iii.3.1). Players have their mixed strategies on the two strategies. Choosing a strategy means that the player considers he should choose this strategy. Justifiability of each strategy is reflected in mixed strategies. Mixed strategies change depending on payoffs of games. Each player is randomly matched with one player and then observes the choice of the opponent. This matching with observation is continuously repeated.

This paper analyzes the dynamics of the mixed strategies. This paper assumes that there are three types of players: sympathy type, fortune type, and virtue type. These types are defined based on payoff matrices. Existence of fortune type characterizes the corruption of moral sentiments. That is why this paper clarifies what fortune type existence implies. Given fortune type existence, the more sympathy type exists in a player set, the more corrupted asymptotically stable points are. The degree of corruption is defined based on the number of players choosing fortune strategy.

References

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