A duty is a moral obligation that an agent has towards another person, such as the duty not to lie. Etymologically, duties are actions that are due to someone else, such as paying money that one owes to a creditor. In a broader sense, duties are simply actions that are morally manditory. Medieval philosophers such as Aquinas argued that we have specific duties or obligations to avoid committing specific sins. Since sins such as theft are absolute, then our duty to avoid stealing is also absolute, irrespective of any good consequences that might arise from particular acts of theft. From the 17th to the 19th centuries, many philosophers held the normative theory that moral conduct is that which follows a specific list of duties. These theories are also called deontological theories, from the Greek word deon, or duty, since they emphasize foundational duties or obligations. We find one of the first clear indications of this view in The Law of War and Peace (1625) by Dutch philosopher Hugo Grotius (1583-1645). For Grotius, our ultimate duties are fixed features of the universe, which even God cannot change, and comprise the chief obligations of natural law. Some moral theorists at the time based their list of duties on traditional lists of virtues.
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Traditional Duty Theory
In On the Law of Nature and of Nations (1672), German philosopher Samual Pufendorf (1632-1694) refined three particular components of duty theory. First, Pufendorf adopts a position that scholars now call "the correlativity of rights and duties." On this view, every right that I have implies a duty on your part to respect my right. For example, if I have a right to own my car, then you have a duty not to steal my car. From a moral standpoint, Pufendorf believed that duties were more important than rights. Second, Pufendorf distinguished between perfect and imperfect duties. Perfect duties are obligations that are precisely defined, and dictate our proper conduct everywhere at all times, such as the duty not to steal. Imperfect duties, by contrast, such as the duty to be charitable, are not fixed, but open as to when and how we perform this duty. Third, Pufendorf provided a detailed categorization of all duties into three main groups: duties to God, duties to oneself, and duties to others. In the selection below, from The Duty of Man and Citizen (1673), Pufendorf argues that duties to others are the most foundational of the three, since this most immediately follows the mandate of natural law that we are to be sociable. Concerning our duties towards God, he argues that there are two kinds: (1) a theoretical duty to know the existence and nature of God, and (2) a practical duty to both inwardly and outwardly worship God. Concerning our duties towards oneself, these are also of two sorts: (1) duties of the soul, which involve developing one's skills and talents, and (2) duties of the body, which involve not harming our bodies such as through gluttony or drunkenness, and not killing oneself. Concerning our duties towards others, Pufendorf divides these between absolute duties, which are universally binding on people, and conditional duties, which are the result of contracts between people. Absolute duties are of three sorts: (1) avoid wronging others; (2) treat people as equals, and (3) promote the good of others. Conditional duties are far reaching and involve every aspect of social contracts and agreements. The first of these is to keep one's promises.
