Here is a picture of ethics. We are designed to operate with a specific algorithm A for generating imperatives from circumstances. Unfortunately, we are broken in two ways: we don’t always follow the generated imperatives and we don’t always operate by means of A. We thus need to reverse engineer algorithm A on the basis of our broken functioning.
In general, reverse-engineering has to be based on a presumption of relative simplicity of the algorithm. However, Kantian, utilitarian ethics and divine command ethics go beyond that and hold that A is at base very simple. But should we think that the algorithm describing the normative operation of a human being is very simple? The official USA Fencing rule book is over 200 pages long. Human life is more complex than a fencing competition. Why should we think that there are fundamental rules for human life that can be encompassed briefly, from which all other rules can be derived without further normative input? It would be nice to find such brief rules. Many have a hope of finding analogous brief rules in physics.
We haven’t done well in ethics in our attempts to find such brief rules: the Kantian and utilitarian projects make (I would argue) incorrect normative claims, while the divine command project seems to give the wrong grounds for moral obligations.
It seems not unlikely to me that the correct full set of norms for human behavior will actually be very complex.
But there is still a hope for a unification. While I am dubious whether one can find a simple and elegant set of rules such that all ethical truths can be derived from them with no further normative input, there may be elegant unifying ethical principles that nonetheless require further normative input to generate the complex rules governing human life. Here are two such options:
Natural Law: Live in accordance with your nature! But to generate the rules governing human life requires the further information as to what your nature requires, and that is normative information.
Agapic ethics: Love everyone! But one of the things that are a part of love is adapting the form of one’s love to fit the the persons and circumstances (fraternal love for siblings, collegial love for colleagues, etc.), and the rules of “fit” are extremely complex and require further normative input.
