Human nature refers to the distinguishing characteristics, including ways of thinking, feeling and acting, that humans tend to have naturally, independently of the influence of culture. The questions of what these characteristics are, what causes them, and how fixed human nature is, are amongst the oldest and most important questions in western philosophy. These questions have particularly important implications in ethics, politics, and theology. This is partly because human nature can be regarded as both a source of norms of conduct or ways of life, as well as presenting obstacles or constraints on living a good life. The complex implications of such questions are also dealt with in art and literature, while the multiple branches of the Humanities together form an important domain of inquiry into human nature, and the question of what it is to be human.
The branches of contemporary science associated with the study of human nature include anthropology, sociology, sociobiology, and psychology, particularly evolutionary psychology, and developmental psychology. The "nature versus nurture" debate is a broadly inclusive and well-known instance of a discussion about human nature in the natural sciences.