Subjective "Morality" and Objective Morality

I have encountered elsewhere a common argument for the subjectivity of morality that really makes no sense. I have presented this response before but, perhaps, I have learned how to present it better.

(1) Whether or not something is moral or not depends on the definition of "moral".
(2) The definition of "moral" is arbitrary and subjective.
(3) Therefore, whether or not something is moral is arbitrary and subjective.

It looks like a good argument. But, consider this:

(1) Whether or not Pluto is a planet or not depends on the definition of "planet".
(2) The definition of "planet" is arbitrary and subjective.
(3) Therefore, whether or not something is a planet is arbitrary and subjective.

We can show that the meaning if the term "planet" is arbitrary and subjective by looking at its history.

Before August 24, 2006, "Pluto is a planet" was a true statement. It was an objectively true statement, and many students got marked as being "wrong" if they failed to identify Pluto as one of the nine planets.

On August 24, 2006, the proposition became false.

This change did not come about because Pluto suffered some catastrophic event that shattered it into countless small parts. The intrinsic properties of Pluto did not change as all.

What happened is that some small number of astronomers vested with authority to make such a decision voted to change the definition of "Planet." Under this new definition, Pluto did not qualify.

The types of arguments people brought to the vote were:

In favor: We should (ought to) classify like objects with like and Pluto is more like other large Kuiper Belt Objects.

Against: We would upset a bunch of people, particularly young children, who have a sentimental attachment to the idea that Pluto is a planet - and we should not do that.

Whether an astronomer voted for or against the change depended on their personal sentiments - on what was important to them.

The change, to a large degree, was arbitrary and subjective.

Yet, nowhere did we hear the argument that astronomy ceased to be a hard science, that its claims ceased to be objectively true or false.

In other words, whether "Pluto is a planet" is true or false depends on what you mean by "planet", and the definition of "planet" is arbitrary and subjective. Yet, nobody argues that this condemns astronomy to subjectivity - that there are no objective astronomical facts.

Why, then, does the argument fail?

What people seem to remember when they discuss science, that they forget when they discuss morality, is that ALL definitions are arbitrary and subjective. Language is an invention - we make it up as we go along.

To preserve objectivity, we need to follow two rules.

(1) Whatever definition we arbitrarily and subjectively decide upon, for whatever reason, we use the term consistently.

(2) We do not use the term to import any property to that which we are referring to that it does not already have. If you claim in your definition that the term refers to objects that are round, and you use the term to refer to something that is not round, then that is a mistake.

It does not matter how we define moral terms - as long as we use the term consistently and, when we call something "moral", we are not assigning to it a property that it does not in fact have (such as an intrinsic property of "ought to be doneness").

Often, when people say that morality is subjective, it seems to be the case that they are using this to legitimize the practice of ignoring the second rule above. They do want to assign a property of "ought to be doneness" to something that does not exist. Rather than saying that using a term that means "having an intrinsic ought-to-be-doneness" to something that does not have it is objectively false - which it is, they want to claim that it is "subjectively true" or "true for me".

In fact, it is "subjectively true" in the same way that the earth is 6000 years old is "subjectively true". It is objectively false.

Anybody who acts as if such a statement is true - and says that this is legitimate because it is "true for them" - is, in fact, objectively wrong, and should be regarded as such.