With currently an estimated 375 million of people in the world who do not eat meat (4.9% of the world population), vegetarianism has come a remarkably long way. Where in ancient times religion often was a motivation to avoid the consumption of meat, the roots of vegetarianism are in fact inspired by philosophy. The Greek and Roman poets Hesiod, Plato and Ovid were among the first to propose vegetarianism as a life style, and two centuries later, the Neoplatonic philosopher Porphyry of Tyre (233-305 AD) wrote an essay on vegetarianism in which he rejected the consumption of meat as it was ‘unjust to eat a sentient animal’. Where French philosopher René Descartes (1596-1650) was not fond of humanitarian attitudes towards animals, the polymath Leonardo da Vinci (1452-1519) did support these type of animal-friendly attitudes, as he was one of the people that questioned the superiority of humans to animals (Chemnit & Becheva, 2014) (Jones, 2011). Emanuel Kant (1724-1804) argued that cruel acts towards animals are inhuman as they damage a human in himself, as if he is inhuman to animals it becomes hard to show humanity towards fellow humans (Gruen, 2017).

Where the ancient motives for not eating meat were mostly ethical and spiritual, more recent philosophical arguments also contain anti-speciesism, anti-carnism and animal-rights (Ruby, 2011). In contemporary and Western society, an even wider variety of motives to become a vegetarian have been established. The most prevailing motives are clearly specified in a comprehensive 2016 German research project. This research shows that animal welfare-related concerns are the most recurrent motivation (89.4%) to become a vegetarian. Another important motive for not eating meat are self-related concerns (69.3%), such as care for personal health. A third motive is found in environmental concerns (46.8%), as research shows that climate change is caused to a large extent by the overconsumption of meat (Walsh, 2016). A less mentioned, but equally important motive is related to social justice-related concerns (10%), where vegetarians take the exploitation of human beings in the meet industry (Human Rights Watch, 2005) into account in choosing their motive for not eating meat  (Janssen, Busch, Rodiger, & Hamm, 2016). Comparable results are found in a 2007 worldwide literature study on the reasons why people turn to a vegetarian diet, although here health-related motives are mentioned as the most common reason to become a vegetarian, followed by animal welfare. Religion is also mentioned as an important motivation (Ion, 2007), whereas it seems that this motive is most commonly seen outside Europe, such as in India, where the predominant religions Buddhism and Jainism put high emphasis on respect and non-violence towards all forms of life (World Atlas, 2017).

Just as interesting in the German study are people’s attitudes in their choice for vegetarianism. 82.2% of the respondents agreed with the statement ‘Animals have similar feelings and fears as humans’, 80.2% agreed with ‘All animal should be granted the right to a natural death’ and a smaller percentage (32.8%) agreed with ‘People should not keep animals at all’ (Janssen, Busch, Rodiger, & Hamm, 2016). These attitudes show a clear direction towards a way of thinking where people consider animals as equal species, or as species that should be treated in the same way as we should treat fellow human beings. This is in line with the ideas of well-known animal rights activist and moral philosopher Peter Singer (1979), as he argues that the concept of equality does not only apply to human beings, but should also be extended to the animal species. Singer motivates his principle by the ethical axiom that even if species are not official members of our race, this does not entitle us to exploit them, just as the ethical axiom that the interests of people less intelligent cannot be disregarded (Singer, 1979).

This brief introduction on the history and motives of vegetarianism shows that vegetarianism can be founded on various religious and philosophical thoughts. The latter can consist of animal welfare-related moral arguments, which includes the idea of equality between humans and animals, the view that we are not allowed to harm and/or kill animals and the belief that animals share similar feelings as humans do. This kind of vegetarianism based on animal welfare-related arguments is the central focus of this paper and will be referred to as moral vegetarianism.

To examine the extent to which morality influences people’s individual choice for vegetarianism I will use Lawrence Kohlberg’s (1977) theory on moral development. I will embark this challenge by giving a brief description of Kohlberg’s comprehensive theory, followed by an extensive analysis on the relationship of his theory with vegetarianism. Next, I will describe the outcomes and possible objections of this analysis, including the related counterarguments. In the conclusion of the paper I will propose an answer to the main question of this paper: how can Kohlberg’s theory of moral development be used to expand vegetarianism? The conclusion consequently includes some recommendations based on the outcomes of the analysis in this paper.

The choice to eat or not eat meat and the six stages of Kohlberg’s theory

Lawrence Kohlberg adopted theories of Jean Piaget (1896-1980) to develop an advanced model of moral development in order to explain moral behavior of individuals. This model does not only show how knowledge of cultural values leads to higher levels of moral development, but also how moral values are developed by the transformations in an individual’s form or structure of thought. According to Kohlberg, universal studies on hypothetical moral dilemmas have shown how the cognitive development of moral reasoning is dividable into three different levels, each separated in two sub stages. These stages are hierarchical and there is a tendency towards a preference for a higher stage. Kohlberg claims that the likelihood of reaching a higher stage of moral development is increased if an individual often encounters moral situations that are not resolved in a satisfactory manner. Empathy has an important role in all these stages of moral development (Kohlberg & Hersh, 1977).

I will include descriptions of each stage in Kohlberg’s theory in the following analysis on the relationship between moral development and vegetarianism. The analysis will be focused on a hypothetical individual who appreciates meat consumption and learns about the possibility of becoming a vegetarian.

The first level of moral development

Imagine the individual at the first level of her moral development, the pre-conventional level, where behavior is judged on the immediate and/or physical consequences of the behavior. In stage I, the punishment and obedience orientation, where in Kohlberg’s theory the individual is considered to be a child, she will balance eating or not eating meat exclusively on the presence or absence of a form of punishment. The parents of the child might prohibit the consumption of meat and will promptly rebuke the child if she secretly eats meat, preventing the further consumption of meat. However, if the parents have no problems with eating meat and the child receives a benefit from meat eating (satisfaction or contentedness, as the child likes meat), nothing will stop the child to eat meat. In this case there is no reason for the individual to become a vegetarian.

A comparable situation can be imagined when the child finds herself in stage II, the instrumental relativist orientation, where the child will balance eating or not eating meat only on the reciprocity when she stops meat consumption. For example, when the child receives a ten minute longer lunch break at school every time she avoids the consumption of meat, then this can be a sufficient reason for the child not to eat meat. However, if there is no form of direct reward (a reward in the form of health benefits is not immediate enough), again, there is no reason for the child to stop eating meat.

Looking at the above description of the first two stages, it can be argued that an individual in the first level of her moral development will not take any moral arguments or values in consideration regarding the choice to eat or not to eat meat.

The second level of moral development

Now imagine the individual in her second level of her moral development, the conventional level, where behavior is judged on the opinion and needs of other individuals. In stage III, the interpersonal concordance orientation or ‘good boy – good girl’ orientation, the individual will balance eating or not eating meat based on her social environment. This means that if her environment approves the consumption of meat, there is no good reason for the individual to stop eating meat. Vice versa, if the majority of her social environment puts high value on vegetarianism, the chance is much higher for the individual to stop eating meat, as Kohlberg’s theory accentuates the perception of others in the form of ‘she means well’ or ‘she does good’ (by not eating meat).

If the individual finds herself in stage IV, the ‘law and order’ orientation, the social environment also includes the (political) authority, society’s fixed rules and the maintenance of social order. This means that the choice between eating or not eating meat will now be based on how the society looks at vegetarianism and/or animal welfare. If the individual lives in a society where eating meat is considered to be completely normal and accepted, the chance of becoming a vegetarian is therefore significantly lowered, and vice versa again, in a society where vegetarianism is appreciated and valued as a good thing, the individual might become a vegetarian due to the society’s positive perception towards vegetarianism[1].

The third level of moral development

Imagine the individual in the third level of her moral development, the postconventional level, where behavior is judged on the individual’s own values and principles, partly or completely separated from the perceptions of family, groups and society as described earlier. In stage V, the social contract, legalistic orientation, the individual will balance eating or not eating meat on critically examined values of the society (how does the society values the well-being of animals?), combined with freedom to personally agree or disagree with these values. Now there are two situations in which it is likely that the individual will stop eating meat. If the society values animal welfare (1), the individual could agree with these values and therefore chooses to become a vegetarian. However, if the society does not put high value on avoiding the consumption of meat by not considering animal welfare as an important merit (2), the individual might think that this point of view should be changed based on rational considerations or social utility (which is why this stage differs from stage IV). This disagreement can prevent the individual from eating meat.

In stage VI, the universal-ethical-principle orientation, the individual will balance eating or not eating meat on self-chosen ethical principles based on logic, universality and consistency. As Kohlberg argues, these principles are more abstract and ethically founded than the concrete moral rules and perceptions of previous stages. Personal conceptions of justice, equality and dignity are the foundation for the advanced principles of stage VI. This foundation relates to some of the more ‘humanistic’ arguments for not eating meat which were pointed out earlier in this paper, such as equality between humans and animals, environmental protection and social justice. This means that an individual in the highest stage of moral development is capable of developing her own principles on how we should treat animals. She will assemble ideas on eating meat based on her own advanced ethical reasoning, keeping into account all ramifications of meat consumption. For example, an individual might construct ideas on equality just as Peter Singer (1979) has argued for (concepts of equality cannot be limited to humans), or an individual can make the following philosophical deliberation to develop a motive for not eating meat:

  1. If a practice causes serious harms that are morally unjustified, then that practice is morally wrong.
  2. The practice of raising and killing animals for food causes serious harms to animals and some human beings.
  3. These harms are morally unjustified.
  4. Therefore, the practice of raising and killing animals for food is wrong.

 This reasoning as quoted from Dan Hooley and Nathan Nobis (2016) uses the general principle ‘it is wrong to cause serious harms that are morally unjustified’ as an argument for avoiding meat consumption (Hooley & Nobis, 2016). It is exactly this kind of advanced and complex thinking that the individual might use in stage VI to choose for (moral) vegetarianism.

It can be vice versa as well, as the individual’s principles in stage VI can also be constructed by thoughts of Nick Fiddes (1991) that a belief in human domination of the non-human world can legitimate eating meat (Fiddes, 1991). Here a deeper belief in the hierarchal position of humans on earth could present a reason to continue meat consumption. Another example of complex thinking that could provide arguments to continue meat eating is given by Michael Martin (1976), as he questions ‘animals their right to life’ by using Michael Tooley’s (1973) assertion that having a right to life is the same as being a person. Following this logic, something that is incapable of understanding the concept of a self cannot be considered as a person, which implies that animals would not necessarily possess the right to life or the right not to suffer (Martin, 1976). Following this reasoning, the consumption of meat would be justified.

Outcomes, objections and replies

There are four outcomes that can be drawn from the above analysis. Firstly, it seems that ethical and animal-welfare-related motives for becoming a vegetarian are mostly found in the third level of moral development, such as Singer’s thinking on human/animal-equality. This intrinsically created reasoning can be the cornerstone for moral vegetarianism. Less ethical reasons are more likely to be found in the second level of moral development, as these stages include more extrinsically focused reasons for becoming a vegetarian, such as society’s conception of eating meat.

Secondly, the analysis provides reasons to believe that the theory of empathy-altruism is correct. This theory by Daniel Batson (1981) states that helpful actions are guided by the capacity to see another individual’s perspective, apart from if they are kin or not (Batson, Duncan, Ackerman, Buckley, & Birch, 1981). To explain the connection of this theory with moral vegetarianism, we must first establish the following definitions of empathy and altruism (Oxford Dictionaries, 2017):

  • Empathy: ‘the ability to understand and share the feelings of another’, i.e. understanding someone else’s perspective;
  • Altruism: ‘disinterested and selfless concern for the well-being of others’.

Usually, if we assume Darwin’s theory on kin selection/altruism to be true, humans tend to predominantly show altruistic behavior towards individuals that are within or close to their own kin (Hodge, 1874). However, the individual who avoids meat consumption out of a genuine concern for the welfare of animals, extends her altruistic behavior far outside human beings, showing an impressive capability to see the perspective of species that are vastly different than herself, i.e. demonstrating a high level of empathy. Thus, moral vegetarianism seems to increase the veracity of Batson’s theory, as this kind of vegetarianism shows that altruistic behavior does not necessarily has to be affiliated with kin-relationship. Additionally, considering that empathy is key in Kohlberg’s theory (Kohlberg & Hersh, 1977), it can be claimed that individuals in stage V and VI need a high capacity of empathy if their principles for not eating meat are based on the welfare of animals. After all, these principles can only be developed if these individuals understand the far-reaching consequences that meat consumption has for animals.

Thirdly, the analysis shows that reaching a high level of moral development does not necessarily mean that an individual will choose to become a vegetarian. The complex moral thinking that is developed in this last level can also lead to deeply substantiated principles to do eat meat, such as those of Martins or Fiddes.

Finally, there is an interesting observation to be made on stage IV when we combine this stage with per country data on the presence and quantity of animal laws and per country data on the number of vegetarians. For example, 9% of the United Kingdom population is now to be considered vegetarian (ranked 7th in the world) (World Atlas, 2017), where at the same time the UK is considered to be the 3rd best country for animal welfare in the world (World Atlas, 2017). Thus, looking back at the logic explained in stage IV earlier, this can indeed provide a strong indication that if the society in which an individual lives puts high emphasis on animal welfare, and the individual finds herself in stage IV of her moral development, the odds are higher that she becomes a vegetarian.

Some of these outcomes are open to criticism. By stating that animal-welfare-related reasons for becoming a vegetarian are mostly found in the third level of moral development, the assumption can be made that all people who base their reasons for not eating meat on animal-welfare-related reasons find themselves in the third level of moral development. This assumption can be objected to as, firstly, this is not in line with Kohlberg’s claim that most people will not go higher than the second level of moral development (Kohlberg & Hersh, 1977) and, secondly, it would put these vegetarians (including myself) on a pretentiously high pedestal.

My response is that it is indeed not true that people who base their choice on these ethical arguments for becoming a vegetarian are all in the highest level of moral development, as they only predicate their choice on these arguments; they do not construct these arguments themselves. If an individual avoids meat consumption because she believes in arguments given by Singer or Hooley and Nobis, the individual does this out of a duty or concession to her social environment or society where these arguments are derived from. Or in other words, the fact that the reasons for not eating meat are found in the third level of moral development, does not mean that using these reasons puts the individual in the third level of moral development. Hence, most reasons for people who do not eat meat will be refined in the second level of moral development.

This immediately counterargues a possible second objection: how can all vegetarians who base their choice for not eating meat on animal welfare have such an impressive level of empathy? Just as my counterargument to the first objection, I do not want to claim this to be a necessary precondition. Assuming (as we determined before) that most vegetarianism is established in the second level of moral development; the individual does not require such a high level of empathy to empathize with species vastly different from herself. The individual only needs some level of empathy to have a basic perception of the pain and suffering animals go through, and some primary form of elementary thinking to understand theories of Singer and others.

My two counterarguments above could raise one last objection. It might sound too negative to say that even people who become vegetarian out of animal welfare-related motives, are only doing so because of their social environment (stage III) or the society they live in (stage IV). Does this mean that these people do not have intrinsic values for becoming a vegetarian and that therefore most vegetarianism is just shallow compliance with extrinsic factors? In part my answer to that is yes, but with the important caveats that this compliance is not shallow and that there are some intrinsic values present in this process of compliance. As Kohlberg describes in stage III, the perception of others in the form of ‘he means well’ becomes important to people (Kohlberg & Hersh, 1977). In order to fulfil to this expectation of meaning well, it is not just a matter of acting exactly according to that single expectation (which would indeed be shallow), as in every individual’s social surroundings there are more expectations than one, and for individuals in stage IV the expectations from society are added as well. The individual must balance, weigh and choose between different expectations, as no one can fulfill all the expectations that are set by their environment. To make this choice, intrinsic values come into play. This does not have to be the profound and ethical way of complex thinking that is required in the third level of moral development, but it does certainly require personal and intrinsic thinking for choosing one of the expectations. To make a well-founded choice, the individual would need to possess a certain level of empathy, the capability to weigh various (moral) arguments and the competence to understand the values of her environment on animal welfare.


We have seen that the motives for becoming a vegetarian, and especially how these motives have been established, differ per stage of moral development. The first level seems the most extraneous level in the context of moral vegetarianism, as in this level the choice for not eating meat is mostly based on the presence of immediate punishment or the reciprocity of the act. However, when we exclude the first level of moral development, this paper shows that the choice to stop the consumption of meat requires a difficult to complex process of weighing certain arguments and principles. A basic to advanced level of empathy is also needed, although for most people their own social environment or the society they live in have the highest influence on their choice for becoming vegetarian.

As an answer to how Kohlberg’s theory of moral development can be used to expand vegetarianism, the initial main question of this paper, I will outline the following recommendations based on the findings of this paper:

  1. We should increase the use of learning mechanisms such as moral education (Rorty, 1998), to expend people’s level of empathy. If successful, this could result in more people choosing to become a vegetarian, as we have seen in the outcome of the analysis in this paper that empathy is key in developing animal welfare-related motives for not eating meat.
  2. Extrinsic influences such as government campaigns to impart a certain normality onto vegetarianism can have its impact on choices made by individuals in the second level of their moral development, which according to Kohlberg will be the majority of people (Kohlberg & Hersh, 1977). After all, most people will predicate their choice for not eating meat on the perception of their social environment and the society they live in.
  3. Scholars like Singer, who are capable of developing profound principles on for instance animal-equality, should continue developing these theories that can confer feasible arguments appealing on animal-welfare and therewith convince people of the questionable moral side of meat consumption.

Looking at these propositions, Kohlberg’s theory on moral development has turned out to be a very useful instrument for understanding vegetarianism. If we indeed want to expand this promising and progressive moment, the use of this instrument can have strong and positive influence on people’s moral behavior regarding meat consumption.



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[1] Vegetarianism as a duty towards society, see Kohlberg’s theory for the specific details.

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