Ethics is that system of ethics for which moral actions are actions in accordance with the duty and regardless of what the consequences may be (for the one performing the moral duty or for the whole). Deontological ethics is usually contrasted with consequentialist ethics, and is often seen as correcting the tendency of consequentialism to resemble a case-by-case ethics or to end up accepting that “the end justifies the means”.
Deontological ethics usually takes the form of specific/codified rules about what are morally acceptable actions and behaviours. Despite its opposition to consequentialism, however, ethics can also take the form of a consequentialism of rules. That is, the due or duty can be defined as a set of rules that, if followed by everyone, would have the optimal outcome.
According to D. McNaughton the three features of ethics are:
♦ the restrictive imperatives,
♦ the duty relations,
♦ and the choice to forgo supererogatory obligations.
There is a class of duties that arise from specific duty relations that we assume to others. Typical examples are the practice of promising, friendship, and relations to relatives. It is a kind of constraint but differs from general constraints. The characteristic is that they are restrictions of the type e.g.: promise me to you.
This is also very different from the idea of universality, the independence from the particular person that utilitarianism has in contrast. For example, according to the maximization of the universal good it may be considered a moral duty to offer voluntary work in a so-called third world country, while according to the specific relations it may be considered a duty to offer in my own country.
From a metaethical point of view we say that actions have ethical properties. This means that they have properties such as being obligatory, permissible or prohibited. This in itself is a form of moral realism. That is, there are moral theories that are anti-realist and, for example, deny that an act can be assigned in an absolute way the property of being morally right or wrong, and theories that accept the assignment of such properties.
Some theories deny the attribution of ethical properties to actions per se, attributing morality or immorality primarily to intentions rather than to actions, while others consider primarily the effects of actions, rather than the actions themselves or good or bad intentions. Ethical theories that attribute ethical properties to actions are called moral realism, and deontological ethics is usually a form of moral realism. The most widespread form of deontological realism has theological origins.
One of the most important deontological theories, Kantian ethics, nevertheless has the characteristic of not being (meta-ethically) realistic. At least not in the way in which (meta-ethically) realistic traditional-type ethologies consisting of a list of injunctions or laws are (meta-ethically) realistic. This is because Kantian ethics starts from a different metaphysical basis, and not from the metaphysics of the “arbitrary” existence of the morally right.
The metaphysical basis of Kantian ethics has as its main component the connection between morality and reason (the right Logos). This is an element it shares with Aristotelian ethics. Whereas most other philosophical theories do not have this feature of Kantian and Aristotelian ethics, but reduce morality to realms more distant from logic and closer to autonomous realms of “sense of morality”.

SOURCE: D. McNaughton, P. Rawling, Deontology, The Oxford Handbook of Ethical Theory, 2006.