This thesis discusses and defends the possible existence of a universal moral grammar and also lists arguments in favour of this theory. It is based on an analogy to linguistics and on the assumptions that our mind is modularly organized; that there is a moral capacity (the moral module) and that this ability is innate to all of us. At the beginning of the thesis, an explanation or a definition of these terms is given, and they are then put into the context of universal moral grammar. For example, an innate trait or capacity is defined as one that can be explained by reference to biological evolution, but its manifestation still depends on the environment. Modularity of the mind is defined as a specific organization of the mind, i.e. this hypothesis states that our mind is divided into mental modules that have different functions. The thesis also acknowledges some of the objections claiming that, because of the modular encapsulation, modules simply cannot be flexible and sensitive to context – which are essential features of the human mind – and shows how this does not necessarily have to be the case. In addition, it is explained that the theory of universal moral grammar could be analogous to the theory of universal grammar in linguistics and the origins of the tendencies for the development of universal moral grammar are presented. Furthermore, the works of John Mikhail – one of the most prominent propagators of the theory of universal moral grammar – are used to help answer the questions of what universal moral grammar really is and what its goals and methods are, which key issues it deals with, and what its terminology includes. The thesis then lists the most important arguments in favour of the universal moral grammar, it presents the research carried out, and provides answers to some of the objections. Most importantly, the thesis describes in details the process of making moral decisions by presenting all its phases. All important elements that affect the computations on mental representations of human procedures by which we ultimately bring judgment on whether something is morally permissible or inadmissible are mentioned and ellucidated. Based on the information presented and the fact that there are moral intuitions shared by many people irrespectively of their demographic differences, the thesis discusses whether there are universal moral principles – rules, norms, prohibitions, etc. – that can be found in all cultures. At the very end, the evolutionary explanation of morality, and whether and how universal moral grammar can be explained in the context of biological evolution, is discussed.