Explain that a completely deductive approach to ethical theory would be meaningless; there must be propositions that are not derived. This emphasizes the need for a multifaceted approach that goes beyond deductive reasoning and reflects the complexity of human moral experience.
There are many ethical theories. In this article, we’ll show that a completely deductive approach to ethics makes ethical theories meaningless.
Before we get started, let’s assume that all ethical theories can be reduced to propositions. It could be argued that this assumption is not true, but we won’t decide that question. Let’s pause here to consider why the assumption that ethical theories can be reduced to propositions is important. It’s part of an attempt to understand ethical judgments within a logical framework. Many philosophers and ethicists have used this approach to explain ethical judgments more clearly and coherently.
Suppose that a theory can be expressed as a system of propositions, and that the truth or falsity of each proposition is determined in a deductive way. Then judging a new proposition to be true can be understood as adding a new element to the set of true propositions. For example, consider three propositions p, q, and r, and a proposition s that is true if all of them are true. If we already know that p, q, and r are true, then we can determine that s is true. This is the same behavior as if we expanded the set of true propositions to {p, q, r, s} by adding an element s to the existing set of true propositions {p, q, r, r, s}. In other words, when judgments about each proposition are made deductively, the act of judging a proposition is equivalent to expanding the set of true propositions. This applies not only when a new proposition is judged to be true, but also when a new proposition turns out to be false. This is because judging a proposition to be false is equivalent to adding its negation to the set of true propositions.
Ethical theories are no exception. If we assume that ethical theories have a deductive structure, then every ethical judgment can be understood as adding an element to the set of true propositions. However, where ethical judgments differ from ordinary judgments is that ethical judgments require propositions that contain ethical value judgments. In other words, ethical judgments require not only a set of propositions that are already known to be true, but also a proposition that contains an ethical value judgment. But here’s the problem. If we retrace the process of deriving ethically meaningful propositions backwards, we will eventually arrive at propositions that cannot be derived. That is, there must be a proposition that is ethically true but not justifiable.
If the backward inference from a proposition is finite, then it is natural to expect to come up with a proposition that is unjustifiable. This is because the backward reasoning must end at some point. But shouldn’t the backward reasoning be infinite? Let’s assume for a moment that infinite backward inference is possible: imagine a never-ending chain of propositions following a proposition. Some people might find the fact that there are an infinite number of propositions problematic, but it doesn’t matter. This may seem like a far-fetched example, but if we assume that there is some general ethical proposition p that is true, then we can think of an infinite number of propositions that follow from p, such as “after one second, p is true”, “after two seconds, p is true”, “after three seconds, p is true”, and so on, all of which are clearly true. Of course, these propositions are true, but they have little practical meaning. But the point is not that these propositions are practically meaningless, but that they are numerous and contain ethical value judgments anyway. Therefore, the existence of an infinite number of propositions is not the problem.
What is problematic is reasoning without a starting point. Reasoning without a starting point, that goes backwards and forwards infinitely, cannot in itself determine anything true or false. It doesn’t matter if all the links in the chain of reasoning are true or false. On the other hand, consider a chain of reasoning that has a starting point from which it cannot be derived. If we assume that the treatment of a proposition that is true is still true, so that the last proposition in the chain is false, i.e., that the negation of the last proposition is true, then retracing the treatment of each link of the chain, one by one, will eventually lead to the conclusion that the starting point of the first proposition in the chain is false. This is a contradiction, so the last proposition in the chain cannot be false unless it is false. But this can’t happen in an endless chain with no starting point. Even if we assume that the last proposition in the chain is false, the contradiction will never appear, no matter how many times we retrace the chain links. In the end, even if every link in the chain is false, there is no contradiction anywhere. So the chain can be either all true, all false, or somewhere in the middle, with one true and one false. And these propositions, at least in ethics, are useless. For what is the point of determining right and wrong if it can be both right and wrong?
We have now come to the conclusion that propositions that cannot be deduced must exist in a perfectly deductive theory of ethics, and from this it naturally follows that if there is nothing in the theory of ethics other than deduction to guide us, then all the vices and crimes in the world can be ethically right. This would be highly contradictory to everyone’s view of ethics, so as a treatment of the above proposition, we can be sure that there must be something other than deduction in ethical theory. Of course, that something must also be justified.
Needless to say, this something is lacking in many modern ethical theories. Many have made up propositions that are true at will, and then built systems on top of them. For example, different ethical theories come from different cultural and social contexts, each with its own unique set of standards and principles. However, these standards sometimes conflict and are often not universally applicable. There is also a tendency to focus on theoretical perfection at the expense of practicality and real-world applicability. It seems that this something is not easy to find. Until the day comes when we fully understand the brain and therefore fully understand ethics, we will have to live with the unjustifiable as true.
We also need to consider that ethical decisions cannot simply be the result of logical reasoning. Our moral intuitions, emotions, and experiences are a complex mix of factors that contribute to our ethical judgments. These factors are difficult to explain using deductive reasoning alone. For example, consider a moral dilemma in a particular situation: when deciding whether an action is right or wrong, we consider not only logical consistency, but also emotional reactions, social norms, personal values, and more. To understand this complex process of ethical judgment, we need more than deductive reasoning.
Ethical theory therefore requires not only a deductive approach, but a multifaceted approach that reflects the complexity of human moral experience. This means going beyond simply seeking logical consistency and attempting to understand how humans actually make moral decisions. Because ethical judgment is so deeply connected to human nature, it requires philosophical, psychological, and sociological insights to fully understand it. Only such an integrated approach will enable true ethical understanding.
