Introduction {#Sec1} ============ Societies often have different attitudes toward how people should live their lives and what their responsibilities are (for example, respecting others' decisions; ref. ^[@CR1]^). These value differences have led to the emergence of *cultural* moral communities: groups of people that believe in, and apply, different moral standards. Moral communities with diverging stances toward the use of coercion have emerged independently of one another within the vast majority of societies, resulting in cultural 'clusters' of communities that share similar moral beliefs and attitudes. For example, members of such moral clusters would condemn people in general for violating others' rights, but also apply varying standards to different groups of people: their own group of co-nationals, especially those sharing the same race or ethnicity, but also people from their own country who happen to differ in race or ethnicity^[@CR2]^. Similarly, within a moral community with more permissive attitudes toward the use of coercion, people may condemn people in general for violating other's rights, but may not accept the use of coercion against people who are from the same racial or ethnic group^[@CR3]^. The existence of moral clusters has been demonstrated in all regions of the world, across all income levels, and in both Western countries, such as the United States and the United Kingdom, and non-Western societies, such as Saudi Arabia, Iran, Indonesia, and Pakistan^[@CR2],[@CR3]^. The existence of value differences has also led to the emergence of *national* moral communities, which emerge around nations---large-scale collectives of individuals sharing common traditions and beliefs and a national identity. National moral communities can be described as national societies with moral codes that define how people should interact with one another in certain situations^[@CR4]^. An example of such moral codes is a 'constitution' that defines how individuals should interact with the state. However, these national moral codes also include more informal aspects of the nation's moral code, such as how individuals should treat one another as members of the nation (for example, should they respect each other's wishes?). As members of national societies, we can describe the people living within them as citizens. Citizens have been shown to hold their state in high regard and to be strongly attached to it (often also because of the nation's language, culture, etc.). When people from the same national culture are under threat, they are often extremely sensitive to such dangers^[@CR5]^. They may also develop strong emotional ties to the nation, and may even sacrifice their lives in order to protect it from harm. In other words, citizens are more likely than non-citizens to support their nation-state's actions even when they violate people's rights. Moreover, these nations are in turn typically more accepting of, and more protective toward, their own citizens than foreign non-nationals---citizenship thus also has a moral valence: a country will be more protective and have a more positive attitude toward its own citizens than toward other foreigners. Because both moral clusters and nations develop around shared cultural values, both the degree to which they support the use of coercion (by which we mean here the use of violent force or threats thereof) and the degree to which they approve of violence as a general rule tend to correlate: the more moral clusters and nations endorse violence, the more likely they are to also be more accepting of violence in specific situations. Thus, it is not surprising that most moral clusters have also adopted the use of violence as a means of addressing people whose beliefs do not match with those of their group^[@CR6],[@CR7]^. For example, societies endorsing more severe consequences for individuals who do not conform to their standards (and thereby accept the use of violence against such people) may also be more likely to support the use of violence in other areas (such as the use of force for the enforcement of law). Moreover, these countries may also be more likely to support violent behavior toward non-citizens (and not just members of their own national group) than countries without such a moral code^[@CR8]^. People living in these countries might also be more accepting of violence in general, such as the use of violence by their country to enforce the law in less-favored regions of their own country^[@CR9]^. As noted above, both value differences and moral communities have been shown to result in specific cultural moralities that dictate what is acceptable and unacceptable. Such specific cultures are often characterized by a specific moral code^[@CR10]^; and the higher the moral acceptance of violence toward outsiders, the higher the cultural value on using force^[@CR11]^. When examining violence worldwide, we can see many examples in which these forces operate (for example, the use of violence against women, the need for political control, or the acceptance of violence toward the country's own people) and in which these forces have led to different levels of violence in different societies. However, we can also see the effect of moral standards on violence in other ways. For example, countries with a particular moral standard often also share cultural values, such as the belief that males have more right to take action than females (because of biology, religion, etc.). In other words, societies that condone violence toward women in one area, for example, may also be more likely to condone violence toward women in other areas (such as in the area of divorce, inheritance, etc.). Furthermore, even when gender equality is legally enforced, and no more than a small amount of violence against women is deemed acceptable, those attitudes can be related to higher overall violence (for example, against men and against women). Here we argue that, for these countries, the morality that characterizes them and is reflected in the laws and other formal aspects of their systems of law is not reflected in a similar moral code that affects the level of violence in the society. We call this the 'dark side of morality.' More specifically, we propose that:The more a country's moral standards allow for the use of violence to enforce laws, to punish violations, and to enforce their specific moral code, the more likely that country is to suffer from high overall levels of violence.The more specific culture of a country that allows for the use of violence to enforce laws, to punish violations, and to enforce its specific cultural values, the higher the level of overall violence in the society.Moral codes (such as those that accept violence for the enforcement of laws) and other cultural values (such as religious beliefs) are likely to be more accepted when people are free of direct sanctions, when the government does not enforce certain moral standards and when there is a feeling of freedom from fear of reprisal and harassment.When individuals are free from fear of reprisals for expressing themselves freely (for example, with respect to their opinion or expression of their beliefs), they feel they have more freedom of expression and a higher level of freedom, and therefore tend to speak their minds without fear of reprisals. This effect is further enhanced if individuals have less to fear of harassment (for example, if the society is a democracy in which the laws of the country are enforced and all beliefs and opinions can be expressed). In other words, these forces may all result in violence in society, but they can also lead to more or less violence in the society. When one speaks of morality in a group, they refer to the moral code adopted by the group, and its acceptance by the group's members (this is not always the case, as in some societies morality is not necessarily a widely accepted set of values). Here we speak of moral codes and cultures as moral codes and cultures, because some moralities can affect the level of violence regardless of people's feelings and convictions. For example, a country can reject violence and adhere to other standards and the effect on overall violence can be less or more than what the moral code allows. In such a case, it is important to analyze which moral code is most accepted in the country (but it may well be that a moral code does not necessarily correspond to its level of acceptance by its society, and that the more moral code that people follow, the more violence they will accept). Moreover, it is also important to examine the level of violence a country allows (even though it may not necessarily have any connection to how prevalent that type of violence is). The dark side of morality: the relationship between specific cultural values and violence {#Sec2} ------------------------------------------------------------------------------------------ We should point out, however, that the level of violence in a society may be more affected by other factors. First, as noted above, a country's moral codes may not correspond to the level of violence in that country. For example, a country with a moral code that sanctions violence against some group may have more than average violence in that group, but lower overall violence in the society. Second, the country may adopt a certain moral code to enable its citizens to better live under that particular form of government. For example, a country adopting religious principles as part of its political principles may also feel obliged to use their religions to oppress their own citizens, such as by sanctioning their imprisonment in the concentration camps of an authoritarian regime. In other words, a country's level of violence toward its own citizens may be determined not only by a particular moral code that it has adopted, but also by whether it has such a code or not, and by how it adopts and implements such a code. For example, countries that approve of violence against women have (in our view) more freedom of movement for the freedom of expression and movement than women living in non-violence-endorsing countries (see the discussion above). There are countries (such as Saudi Arabia) that have laws that enable people to kill others who