Introduction This paper is an analysis of the theory of moral rationalism. The analysis explores how this theory contributes to the debate about euthanasia. This theory holds that individuals’ actions should always be guided by reason. For instance, it is morally wrong to stop somebody without a good reason. Honesty is the general rule, but it is subject to many exceptions given that people live in a pragmatic society. Euthanasia is a controversial topic as it entails several moral dilemmas that demand careful consideration due to its immediate and future consequences. Based on the aforementioned concept, this paper adopts the theory of moral rationalism to develop the direction of arguments. This paper will argue that based on reason and the state of medical advancement in contemporary times, there is no need for mercy killing, and thus euthanasia should not be tolerated. Moral rationalism Moral rationalist theories argue that human beings’ behavior is guided by reason. Also, these theories, which are also commonly referred to as ethical rationalism, are based on the practical reason that entails determining how to achieve one’s objectives. Moreover, the theories dictate the objectives that should be prioritized. In this perspective, immoral actions should not be mistaken as contradicting beliefs, but a conflict in the will. This assertion explains why some people will take opposing choices since practical reasoning can be objective as well as universal. Human behavior largely comes from the moral rational choices that human beings make in life. This theory addresses the question of why human beings should be moral. When solving various ethical issues, it can be shown that morally rational behavior leads to ethical deportment during practice. For example in the case of euthanasia, medical practitioners have to act morally because it is simply out of reason that they have to act so. Human beings rely on the available evidence to generate beliefs about life and goals that should be attained, and thus the use of reason leads to success in these objectives. This theory has direct relevance to ethical issues; hence, it is necessary to examine how reason is applicable in solving some of the persisting debates on ethical dilemmas. Euthanasia Euthanasia or mercy killing is a situation where someone is terminally ill with the disease and s/he can determine his/her fate either voluntarily or via an accomplice. The process of mercy killing takes various forms such as administering lethal injections, ending treatment, or isolation. Euthanasia is of different kinds, which include voluntary euthanasia, whereby the procedure is advanced with the consent and expressed desire of the victim. Second is non-voluntary euthanasia whereby the practice is conducted when the victim is incapacitated to make a decision or s/he needs to be protected from him/herself. Last is the involuntary euthanasia when the procedure is done against the will of the victim. Deliberate advancement of a patient’s death by whichever form has no justifiable benefit to that person. A let live decision should be the debate since medical technology has greatly advanced and research is still ongoing to find cures for the terminal diseases. Although the doctors’ code of ethics does not support mercy killing, it remains a controversy, which no doctor has shown the abil