My belief is that there can be no objective ethics, because in order for their to be objective ethics, we must eventually make an assumption as to what is ultimately important, e.g. we could say life is sacred, and thus it is unethical to arbitrarily take away life.

However even the notion that life is sacred is just a bi-product of the evolution process, and in addition, the claim is not scientific, because one cannot perform an experiment to test the assumption that life is sacred or not.

Despite this, I have met many people who are of the belief that ethics is objective. Is there a rational argument that can support this view?

  • 4
    Tricky subject. There are "rational" arguments sure, but "rationality" is subjective (i.e., the arguments are only rational to some people), or perhaps only logically sound when following a particular logical system (one which you may not ascribe to). So are there rational arguments? Sure. Theologians and philosophers have pushed several in history (most memorable for me was Kant's attempt). Have any ever convinced me? No...
    – stoicfury
    Nov 16, 2013 at 9:14
  • 1
  • ethics that can be defined are not the true and eternal ethics... Mar 7, 2014 at 11:34
  • Ethics can be objective, see philosophy.stackexchange.com/a/10439/5759 and references therein.
    – alanf
    May 2, 2014 at 9:40
  • You make an assumption that humans evolved, but there was never a formal study that showed conclusively that Indo-European man came from apes or a lower form of life. The findings of proto-humans found in the ground remains anecdotal and may be related to Natives, for example, with a differing history.
    – Marxos
    Aug 5, 2021 at 22:51

7 Answers 7


There are objective things that look like ethics, such as "non-extinction-promoting social behaviors for Homo sapiens" and "generalization of intuitive morality to large-group behavior such that individual intuitive morality is maximally fulfilled".

The problem is mostly not that there is a lack of things which can be said objectively, but that people want more than reality can support when it comes to ethics. (Free will is similar in this regard.)

So if you want ethics to back up your revulsion at something that is supposed to be reviled in our society, it's rather hit or miss objectively. If you want it to make sure humans are around in another 10k or 100k years, and are reasonably content in the meantime, you've got objectivity galore to play with. (Not that we know the answers (yet), but we can ask the questions.)


The only moral theory that ever seemed like it could have any "objective" value was Kant's "Categorical Imperative". The reason it could be considered objective is because the moral value of an action is not determine by some arbitrary intuition, but by logical consistency with a verifiable condition. Here's an heavily simplified summary of the categorical imperative from another question I answered:

Kant's categorical imperative is the basis for one of very few moral theories that attempts to derive morality from purely logical means. (It is possibly the only complete theory to do so). It's power comes from its lack of dependence on unsound habits and unjustifiable intuitions. To Kant, an action is morally permissible if and only if its manifestation as a universal is not necessarily contradictory.

The result of applying the categorical imperative to moral dilemmas often coincides with our moral intuitions. It could be argued that the "golden rule", (which most people would intuitively consider moral), is a dumbed down version of the categorical imperative. However, the categorical imperative arises out of logical necessity (infallible), whereas the "golden rule" arises out of intuition.
  • if you downvote you should leave a comment Mar 12, 2014 at 15:45

I (almost) agree with you on the subjective nature of ethics. However, subjective nature of ethics does not imply that there can be nothing near-universal in the moral principles of different people and societies. Some of these principles - such as the imperative to care for young children - appear almost universally for evolutionary reasons: societies where caring for the young is uncommon would perish in very short term.

In other words, the claims for objective ethics could be caused by the near-universal commonalities in personal ethics', those commonalities being caused by evolutionary drive. In particular, Mills-style utilitarianism seems to be a reasonable model of ethics because it defines ethics as maximization of the society's well-being, and therefore is most suited to reflect the evolutionary drive that causes the commonalities among personal ethics' of the members of the surviving society.


It depends on how you define "sound". If purely rational then the answer is no. The same goes for purely intuitive. The reason is ethical reality is not knowable by pure reason. Objective ethics (OE) could only be based on freedom. But freedom is paradoxical. 1) Freedom is no less objective than determinism. It is independent of any particular subject and at the same time it depends on him. 2) Freedom is the ultimate goal, ie freedom is what is ultimately important. But the goal of freedom is freedom itself. 3) Freedom is impossible to study or to define rationally but at the same time we all feel it.

As my English is poor, I simply refer you to the book "Cult of Freedom & Ethics of Public Sphere". From the book description: OE is the basis for actions of and relations between any rational beings not connected personally. It has nothing to do with religion, traditions or science. The practical norms of OE are found and formed through a trusted fair contract between free moral actors. However, OE is not based on contract. Rather it is contract that based on this ethics.

There is a site dedicated to this topic - http://ethical-liberty.com. It is based on the book and presents all of the important ideas.


You mention "sound" in your title and "rational" in your question. "Soundness" generally refers to an argument being valid and having true premises. "Rational" can mean many different things including but not limited to (a) valid in form and (b) what a reasonable person would believe. I'm going to skip over the problems about parsing whether such a view is rational (you seem to presuppose that it is not in how you structure your question, so this indicates a particular definition of rationality probably closer to (b) where (b) has some relation to a set of core beliefs about human evolution as it relates to society). Things get even cloudier when you add the term "objective."

I think there's an Achilles' Heel in the position that you present which you should consider. Consider the following:

(1) Our thoughts in ethics are products of human biological evolution

This by itself proves nothing.

You need to add something like: (IR) Every thought that is a product of human biological evolution is "irrational."

This would give you your desired conclusion: Therefore these thoughts are "irrational" / "not objective" / "unsound"

The problem with (IR) though is that it seems like it would apply to any thought. E.g.,

(2) Our thoughts that the sun orbits the earth are products of human biological evolution By (IR), they are "irrational" "not objective".

Obviously you see the problem with (IR) as you qualify by adding "just a bi-product ... of evolution" and "not scientific". So you seem to be saying IR':

(IR') Every thought that is just a product of human biological evolution is "irrational."

But the revised (IR') opens problems in two directions:

(1) What makes something just such a product if not that it is arbitrary rather than mapping onto the world? If so, then it seems we should move to (IR''): Every thought that is arbitrary is "irrational". But doing so unlinks the science.

(2) Why should scientific thoughts be privileged on such an analysis? any such answer seems like it will have to appeal to some link to reality which will always be mediated by our grasp of reality which will always be a product of our biological evolution. (In other words, the trust we put in "science" is circularly built on already trusting the basis for science in our thoughts). Thus, it's not really clear how (IR') is better than (IR) since we seem to be smuggling the benefits in without proving why we have a right to distinguish types of thoughts relative to their biological and evolution origins.


Ethics is just a formalization of the tit for that model. An eye for an eye. If it was to be objective it would need to have objective information about the situation to be judged.


Your argument seems to be:

evolutionary theory X -> no objective ethics

You might also consider:

objective ethics -> evolutionary theory X is wrong

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