Question: "What is deontological ethics / deontology?"
Answer: Deontology is the study of moral duty and is one of the major categories of normative ethics. It teaches that ethical behavior starts with an established, defined duty. An act, then, is ethical if it adheres to duty. There is some discussion, however, as to who dictates duty and whether ethical behavior is based strictly on adherence to rules or if the will of the acting agent has a role.
Moral absolutism is unique in secular ethics in that it is the only school of thought that places the standard for morality outside of the judgment of the acting agent. Also, the standard is not dependent on the situation or the outcome of the action. Moral absolutism is based on one of three possible authorities:
Natural Law - Natural law theory is the philosophy that everything in nature is subject to a particular way of acting that will best enable it to fulfill that nature. The law as it applies to humanity is based on human nature and can be determined by carefully considering that universal nature of mankind which is independent of culture and era. Ironically, although natural law is supposedly derived from the universality of human nature, philosophers can't agree on what the key points of natural law should be. They usually include life, procreation, and some kind of personal fulfillment.
Contractual Agreements - Two of the most basic rules in society are that individuals will not harm each other and individuals will not lie. Contractarianism is the belief that a contract or promise automatically gives moral weight to the actions necessary to fulfill that contract. The "contract" may be a voluntarily agreed-upon list of obligations or the assumed responsibilities of a citizen in a society.
Divine Command - The divine command theory states that an action's morality is based on its adherence to the command of God. An act can only be ethical if it obeys God’s law, and the word of God overrides any other law, custom, or inclination.
Kantian duty was developed by Immanuel Kant, who didn't feel that fulfilling a duty was a sufficient standard for morality. Kant believed a moral act must be accomplished deliberately and for the specific intent of fulfilling that duty. To accidentally drop a sandwich in front of a beggar or to donate money as a tax write-off are not ethical acts—the first because it was not deliberate, the second because it was not done with altruistic motives.
Philosophers have also added qualifiers to deontology. Contemporary Deontology teaches that, even if an act is performed out of duty, it cannot ethical if it causes harm to another—unless that harm will bring about a greater good. The Non-Aggression Principle is similar, insisting that violence is only allowed in self-defense.
What deontology does right is that it takes the standard of morality out of humanity's hands and places it in something with absolute authority. Unfortunately, deontologists then argue about the source of that authority. The Bible is clear: God created us with the purpose of having communion with Him (John 15:14-15). To that end, He has given us standards that will lead us into fulfilling our purpose. "Morals" and "ethics" are human words for godly righteousness that reflects the character of God while recognizing His sovereignty and glory. The categories of deontology are just snapshots of God's rule.
Biblically, the whole concept of obedience out of duty is a little off-center. The Bible doesn't give duty as the motivation for right behavior. Exodus 20:6; Deuteronomy 5:10; Joshua 22:5; John 14:15; 2 John 1:6 and eleven other verses associate love for God with obedience. Righteousness, then, isn't about duty or obligation; it's an expression of our love for God.
Still, there are similarities between biblical teaching and deontology. Natural law theory allows for God placing His law in our hearts. Romans 2:14-15 says, "For when Gentiles who do not have the Law do instinctively the things of the Law, these, not having the Law, are a law to themselves, in that they show the work of the Law written in their hearts, their conscience bearing witness and their thoughts alternately accusing or else defending them..." However, five chapters later, Paul states that human nature alone cannot lead us to obey God's rule: "For I joyfully concur with the law of God in the inner man, but I see a different law in the members of my body, waging war against the law of my mind and making me a prisoner of the law of sin which is in my members" (Romans 7:22-23). Relying on conscience or instinct can only take us so far in determining what is good. Natural law is insufficient. We must go directly to God and His Word to get the full picture (Psalm 25:4).
The Bible also contains shades of contractarianism. Numbers 30:2 says, "If a man makes a vow to the LORD, or takes an oath to bind himself with a binding obligation, he shall not violate his word; he shall do according to all that proceeds out of his mouth." And Romans 13:1-7 admonishes us to obey the civil authorities, pointing out that the authorities are there to make sure society acts ethically. So, Christians are obliged to be good citizens. The Bible also condemns foolish oaths. Leviticus 5:4 says a person who swears an oath without thinking about the consequences is still responsible for the outcome. Instead, Jesus suggests we embody such good character that we won't need to make oaths (Matthew 5:33-37).
The Bible definitely supports the idea behind divine command theory. The Logos—the logical Word—created the world; John 1:3 says, "All things came into being through Him, and apart from Him nothing came into being that has come into being." This same Creator has revealed His law to us: “He has showed you, O man, what is good. And what does the LORD require of you? To act justly and to love mercy and to walk humbly with your God” (Micah 6:8). We have the promise of wisdom for the asking (James 1:5) and Scripture, which is "God-breathed and is useful for teaching, rebuking, correcting, and training in righteousness, so that the man of God may be thoroughly equipped for every good work" (2 Timothy 3:16).
The Bible also supports Kant's inclusion of motive as part of the moral standard. Mark 12:41-44 tells the story of the widow who gave her last coins to the temple treasury. Jesus praised her for the spirit of her sacrifice. Deuteronomy 30:2 encourages God-followers to "return to the LORD your God and obey Him with all your heart and soul according to all that I command you today." To “return” and offer heartfelt obedience would require a deliberate act of the will. This doesn't mean that every moral act needs to be intentional, however. Luke 6:43-45 suggests that ethical acts arise from the natural behavior of a virtuous person. It's unlikely that such a person would be cognizant of every one of God's laws he obeys throughout the course of a day.
Deontology is one of several theories of ethics that attempt to narrow the definition of an ethical act into secular, humanistic terms. This doesn't work because "good" and "right" and moral value cannot come from fickle, fallen mankind without absorbing the qualities of fickleness and fallenness. Fortunately, we don't have to rely on ourselves; God has told us what is good, and the righteousness of Christ is the standard of all morality.