Buddhism provides many opportunities for comparative study with a diverse range of subjects. For example, Buddhism's emphasis on the Middle way not only provides a unique guideline for ethics but has also allowed Buddhism to peacefully coexist with various differing beliefs, customs and institutions in countries where it has resided throughout its history. Also, its moral and spiritual parallels with other systems of thought—for example, with various tenets of Christianity—have been subjects of close study. In addition, the Buddhist concept of dependent origination has been compared to modern scientific thought, as well as Western metaphysics.