Moral reasoning, also known as moral development, is a study in psychology that overlaps with moral philosophy. Children can make moral decisions about what is right and wrong from a young age; this makes morality fundamental to the human condition. Moral reasoning, however, is a part of morality that occurs both within and between individuals.  Prominent contributors to this theory include Lawrence Kohlberg and Elliot Turiel. The term is sometimes used in a different sense: reasoning under conditions of uncertainty, such as those commonly obtained in a court of law. It is this sense that gave rise to the phrase, "To a moral certainty;" however, this idea is now seldom used outside of charges to juries.
Moral reasoning can be defined as being the process in which individuals try to determine the difference between what is right and what is wrong by using logic. This is an important and often daily process that people use when trying to do the right thing. For instance, every day people are faced with the dilemma of whether to lie in a given situation or not. People make this decision by reasoning the morality of their potential actions, and through weighing their actions against potential consequences.
A moral choice can be a personal, economic, or ethical one; as described by some ethical code, or regulated by ethical relationships with others. This branch of psychology is concerned with how these issues are perceived by ordinary people, and so is the foundation of descriptive ethics. There are many different forms of moral reasoning which often are dictated by culture. Cultural differences in the high-levels of cognitive function associated with moral reasoning can be observed through the association of brain networks from various cultures and their moral decision making. These cultural differences demonstrate the neural basis that cultural influences can have on an individual’s moral reasoning and decision making .
In 1983, James Rest developed the four component Model of Morality, which addresses the ways that moral motivation and behavior occurs . The first of these is moral sensitivity, which is "the ability to see an ethical dilemma, including how our actions will affect others". The second is moral judgment, which is "the ability to reason correctly about what 'ought' to be done in a specific situation". The third is moral motivation, which is "a personal commitment to moral action, accepting responsibility for the outcome". The fourth and final component of moral behavior is moral character, which is a "courageous persistence in spite of fatigue or temptations to take the easy way out".
Distinctions between theories of moral reasoning can be accounted for by evaluating inferences (which tend to be either deductive or inductive)based on a given set of premises. Deductive inference reaches a conclusion that is true based on whether a given set of premises preceding the conclusion are also true, whereas, inductive inference goes beyond information given in a set of premises to base the conclusion on provoked reflection.
This branch of psychology is concerned with how these issues are perceived by ordinary people, and so is the foundation of descriptive ethics. There are many different moral reasonings. Moral reasoning is culturally defined, and thus is difficult to apply; yet human relationships define our existence and thus defy cultural boundaries.
Lawrence Kohlberg is a psychologist who has made significant contributions to the field of moral reasoning by creating a theory of moral development. His theory is a "widely accepted theory that provides the basis for empirical evidence on the influence of human decision making on ethical behavior." In Lawrence Kohlberg's view, moral development consists of the growth of less egocentric and more impartial modes of reasoning on more complicated matters. He believed that the objective of moral education is the reinforcement of children to grow from one stage to an upper stage. Dilemma was a critical tool that he emphasized that children should be presented with; yet also, the knowledge for children to cooperate. According to his theory, people pass through three main stages of moral development as they grow from early childhood to adulthood. These are preconventional morality, conventional morality, and postconventional morality. Each of these is subdivided into two levels.
The first stage in the preconventional level is obedience and punishment. In this stage people, usually young children, avoid certain behaviors only because of the fear of punishment, not because they see them as wrong. The second stage in the preconventional level is called individualism and exchange: in this stage people make moral decisions based on what best serves their needs.
The third stage is part of the conventional morality level and is called interpersonal relationships. In this stage one tries to conform to what is considered moral by the society that they live in, attempting to be seen by peers as a good person. The fourth stage is also in the conventional morality level and is called maintaining social order. This stage focuses on a view of society as a whole and following the laws and rules of that society.
The fifth stage is a part of the postconventional level and is called social contract and individual rights. In this stage people begin to consider differing ideas about morality in other people and feel that rules and laws should be agreed on by the members of a society. The sixth and final stage of moral development, the second in the postconventional level, is called universal principles. At this stage people begin to develop their ideas of universal moral principles and will consider them the right thing to do regardless of what the laws of a society are.
Another psychologist who contributed to the field of moral reasoning was Jean Piaget. He developed two phases of moral development, one common among children and the other common among adults. The first is known as the Heteronomous Phase. This phase, more common among children, is characterized by the idea that rules come from authority figures in one's life such as parents, teachers, and God. It also involves the idea that rules are permanent no matter what. Thirdly, this phase of moral development includes the belief that "naughty" behavior must always be punished and that the punishment will be proportional.
The second phase in Piaget's theory of moral development is referred to as the Autonomous Phase. This phase is more common after one has matured and is no longer a child. In this phase people begin to view the intentions behind actions as more important than their consequences. For instance, if a person who is driving swerves in order to not hit a dog and then knocks over a road sign, adults are likely to be less angry at the person than if he or she had done it on purpose just for fun. Even though the outcome is the same, people are more forgiving because of the good intention of saving the dog. This phase also includes the idea that people have different morals and that morality is not necessarily universal. People in the Autonomous Phase also believe rules may be broken under certain circumstances. For instance, Rosa Parks broke the law by refusing to give up her seat on a bus, which was against the law but something many people consider moral nonetheless. In this phase people also stop believing in the idea of immanent justice.
Jonathan Haidt is a social psychologist who defines moral as: the sudden appearance in consciousness of a moral judgment, including an affective valence (good–bad, like–dislike), without any awareness of having gone through steps of searching, weighing evidence, or inferring a moral conclusion. Moral intuition is therefore the psychological process that the Scottish philosophers talked about, aprocess akin to aesthetic judgment. One sees or hears about an event and one instantly feels approval or disapproval. Haidt argues that many people do not utilize conscious reasoning to make our judgments.
Gusto Blasi is a moral psychologist who rebuts the theories of Jonathan Haidt on moral intuition and reasoning. He agrees with Haidt that moral intuition plays a significant role in the way humans operate. However, Blasi suggests that people use moral reasoning more than Haidt and other cognitive scientists claim. Blasi advocates moral reasoning and reflection as the foundation of moral functioning. Reasoning and reflection play a key role in the growth of an individual and the progress of societies. Blasi, A. (2009). 
Philosopher David Hume and psychologist Jonathan Haidt both claim that morality is based more on perceptions than on logical reasoning. This means that people's morality is based more on their emotions and feelings than on a logical analysis of any given situation. Hume regards morals as linked to passion, love, happiness, and other emotions and therefore not based on reason. Haidt agrees, arguing that reasoning concerning a moral situation or idea follows an initial intuition. Haidt's fundamental stance on moral reasoning is that "moral intuitions (including moral emotions) come first and directly cause moral judgments"; he characterizes a moral intuition as "the sudden appearance in consciousness of a moral judgment, including an affective valence (good-bad, like-dislike), without any conscious awareness of having gone through steps of searching, weighing evidence, or inferring a conclusion".
Immanuel Kant had a radically different view of morality. In his view, there are universal laws of morality that no one should never break regardless of emotions. He proposes a four-step system to determine whether or not a given action was moral based on logic and reason. The first step of this method involves formulating "a maxim capturing your reason for an action". In the second step, one "frame[s] it as a universal principle for all rational agents". The third step is assessing "whether a world based on this universal principle is conceivable". If it is, then the fourth step is asking oneself "whether [one] would will the maxim to be a principle in this world". In essence, an action is moral if the maxim by which it is justified is one which could be universalized. For instance, when deciding whether or not to lie to someone for one's own advantage, one is meant to imagine what the world would be like if everyone always lied, and successfully so. In such a world, there would be no purpose in lying, for everybody would expect deceit, rendering the universal maxim of lying whenever it is to your advantage absurd. Thus, Kant argues that one should not lie under any circumstance. Another example would be if trying to decide whether suicide is moral or immoral; imagine if everyone committed suicide. Since mass international suicide would not be a good thing, the act of suicide is immoral. Kant's moral framework, however, operates under the overarching maxim that you should treat each person as an end in themselves, not as a means to an end. This overarching maxim must be considered when applying the four aforementioned steps. 
At one time psychologists believed that men and women have different moral values and reasoning. This was based on the idea that men and women often think differently and would react to moral dilemmas in different ways. Some researchers hypothesized that women would favor care reasoning, meaning that they would consider issues of need and sacrifice, while men would be more inclined to favor fairness and rights, which is known as justice reasoning. However, some also knew that men and women simply face different moral dilemmas on a day-to-day basis and that might be the reason for the perceived difference in their moral reasoning. With these two ideas in mind, researchers decided to do their experiments based on moral dilemmas that both men and women face regularly. To reduce situational differences and discern how both genders use reason in their moral judgments, they therefore ran the tests on parenting situations, since both genders can be involved in child rearing. The research showed that women and men use the same form of moral reasoning as one another and the only difference is the moral dilemmas they find themselves in on a day-to-day basis. When it came to moral decisions both men and women would be faced with, they often chose the same solution as being the moral choice. At least this research shows that a division in terms of morality does not actually exist, and that reasoning between genders is the same in moral decisions.
- Raine, A. & Yang, Y. (2006). Neural foundations of moral reasoning and antisocial behavior. Social Cognitive and Affective Neuroscience 1(3), 203-213. doi:10.1093/scan/nsl033
- Victor v. Nebraska (92-8894), 511 U.S. 1(1994), from the syllabus, holding (c) and throughout, available in the Cornell Law School Supreme Court Collection
- "Definition of: Moral Reasoning". Retrieved 21 July 2011.
- Sachdeva, S., Singh, P., & Medin, D. (2011). Culture and the quest for universal principals in moral reasoning. International Journal of Psychology, 46(3), 161-176. doi:10.1080/00207594.2011.568486
- Lincoln, S. H. & Holmes, E. K. (2011). Ethical decision making: a process influenced by moral intensity. Journal of Healthcare, Science and the Humanities, 1(1), 55-69. doi:10.1111/j.1559-2011.tb02661.x
- Lynn E. Swaner, "Ethical and Moral Reasoning," Educating for Personal and Social Responsibility, Position Paper, American Council of Colleges and Universities, September 13, 2004 (pdf), citing James Rest, "Morality," in Cognitive Development, ed. John H. Flavell and Ellen M. Markman, Handbook of Child Psychology volume 3, 4th ed. New York: Wiley, 1983, ISBN 978-0-471-09064-9, pp. 556–629.
- Bucciarelli, Monica; Khemlani, Sangeet; Johnson-Laird, P.N. (February 2008). "The psychology of moral reasoning" (PDF). Judgment and Decision Making, Vol. 3, No. 2. Retrieved 20 July 2011.
- Cherry, Kendra. "Kohlberg's Theory of Moral Development". about.com psychology. Retrieved 20 July 2011.
- Tsui, Judy; Carolyn Windsor (May 2001). "Some Cross-Cultural Evidence on Ethical Reasoning". Journal of Business Ethics. 31 (2): 143–150.
- Musschenga, Albert W. (2009). "Moral Intuitions, Moral Expertise and Moral Reasoning". Journal of Philosophy of Education. 43 (4): 597–613. doi:10.1111/j.1467-9752.2009.00707.x. Retrieved 19 December 2012.
- Walsh, Keiron. "Piaget's Theory of Moral Development". Development of Moral Understanding. Retrieved 11 Oct 2014.
- The Emotional Dog and its Rational Tail: A Social Intuitionist Approach to Moral Judgement (2001), p.818
- The moral functioning of mature adults and the possibility of fair moral reasoning. In D. Narvaez and D. K. Lapsley (Eds.), Personality, identity, and character: Explorations in moral psychology (pp.396-440) New York: Cambridge University Press
- Clopton, Nancy A.; Sorell, Gwendolyn T. (March 1993). "Gender Differences in Moral Reasoning: Stable or Situational?". Psychology of Women Quarterly Vol. 17 No. 1. doi:10.1111/j.1471-6402.1993.tb00678.x. Retrieved 21 July 2011.
- Haidt, J. (2001) The Emotional Dog and its Rational Tail: A Social Intuitionist Approach to Moral Judgement, Psychological Review, 108, pp. 814–34
- Roberto Andorno, "Do our moral judgements need to be guided by principles?" Cambridge Quarterly of Healthcare Ethics 2012, 21(4):457-465.