On Pluto, Planets, and Goodness

It seems that astronomers are still debating the definition of a planet.

I love this debate because it illustrates a point that I have been trying to make in the field of ethics for years.

One argument that I have confronted is the claim that since ethicists disagree on the definition of ‘good’, and there seems to be no experiment that one can perform to determine which definition is correct, that this implies that all of ethics is subjective and that there are no objectively right answers.

Now, we have astronomers who disagree on the definition of ‘planet’, and there seems to be no experiment that one can perform to determine which definition is correct. However, this does not imply that all of astronomy is subjective and that there are no right answers. In fact, this dispute does not threaten the objectivity of astronomy at all.

Once you can understand how astronomers can disagree on the definition of ‘planet’ without threatening the objectivity of astronomy, you can understand how ethicists can disagree over the definition of ‘good’ without threatening the objectivity of ethics.

The reason that this is possible is because what we call Pluto (for example) has no bearing on its mass, its shape, its surface features, its temperature its chemical composition, its orbital properties, and the like. What we call something has no relevance to the question of what its properties are.

It is also the case that what we call ‘good’ has no bearing on its properties and relationships. You can call something ‘good’ if you want to, but it does not cause reasons-for-action to bring about that thing to suddenly spring into existence. And taking away the term ‘good’ does not cause reasons for action to suddenly evaporate. Those reasons for action either exist or they do not exist – quite independent of what we claim to be true about their existence.

Astronomy is objective in spite of the subjective definition of ‘planet’ because Pluto’s properties do not depend on what we call it. Ethics is objective in spite of the subjective definition of ‘good’ because the relationships between states of affairs and reasons for action that exist do not depend on what we call them.

I am entertained by some of the ‘arguments’ that astronomers are using in this dispute over the definition of ‘planet’.

Many planet scientists were disgruntled over the 2006 IAU decision, which they said involved a vote of just 424 astronomers out of some 10,000 professional astronomers around the globe. The most recent decision, to categorize Pluto and such as plutoids, further ticked off many astronomers, who felt the term was developed behind closed doors.

In science, certainly, you do not have worries about whether the Theory of Relativity was decided on by a vote of 424 out of 10,000 physicists, or object to the Theory of Evolution on the grounds that it was developed ‘behind closed doors’. These types of claims simply are not relevant to the truth of scientific theories. These are the marks of people having to deal with subjective definitions.

Yet, the people involved in this debate can leave their office, go back to their telescopes and rock samples, and continue to engage in the wholly objective study of planets.

As well they should.

"We're going to do something that the IAU did not, which is discuss what we know about planetary bodies in the solar system and around other stars, and discuss the value of different ways of defining objects as planets and what that means," said Mark V. Sykes, director of the Planetary Science Institute in Tucson, Ariz. When the dust settles, those involved hope a consensus will stand, a classification scheme for all objects orbiting a star.

And what fact about planetary bodies are we going to look at to determine whether a planet substantially clears its orbit of other objects or not? Where, in the spectral analysis of a heavenly body do we read off the proof that being round due to one’s own gravity and orbiting a star is sufficient reason to call something a planet? Where are they going to find the proof that one definition is correct, and the other is not?

They are not going to find their proof in the same types of evidence that they use to find proof as to the body’s size, or surface features, or temperature. They’re going to discover that they are locked in a debate whose ultimately answer is not going to be dug out of their piles of data. Their ultimate answer depends on the sentiments and preferences of individual astronomers. Their ultimate answer is wholly subjective.

Yet, the objectivity of astronomy survives all of this. And the objectivity survives the subjective definition of ‘good’ just as easily.

What is really happening when a person assigns the term ‘good’ to some state of affairs is that he is trying to get people to create or preserve that state of affairs. He wants them to believe that there are reasons for action for bringing about such a state. However, his ambition to give others this belief does not make the belief true.

We have no parallel in the realm of planets. The types of motives that astronomers might have for pushing a particular definition of ‘planet’ would have to do with sentimental value, or with the possibility that one can get more funding (and prestige) studying something called a planet than by studying something of less significance. However, the definition of ‘planet’ cannot be used to manipulate others the way that a definition of ‘good’ can, so we get a lot less of this from astronomers (or non-astronomers).

The assignment of ‘good’ for these reasons can actually be true or false. If we define S as a state that there exists reasons to bring about or preserve, we should not allow ourselves to be fooled into thinking that we cannot question the claim. We should be wary of the fact that you cannot define reasons for action into existence any more than you can define God or angels or a Pluto that is 8000 km in diameter into existence.

If somebody tries to define reasons for action into existence, we have no obligation to take his definition of ‘good’ at face value. We are perfectly free to say to him, “Either admit that you are attempting to use ‘good’ in a way that has nothing to do with reasons for action, or admit that your use of the term ‘good’ in this instance is flawed since it claims the existence of reasons for action that do not, in fact, exist.”

If ever you should find yourself in a debate with somebody over the objectivity of value, and he claims, “You can’t prove that your definition of ‘good’ is any better than any others,” remind them of Pluto and the definition of a planet. It’s true, when it comes to definitions, that we cannot prove that one definition is intrinsically correct and that all others are inherently wrong. But that is just a fact about the subjectivity of language. It has nothing to do with the objectivity of ethics. The subjectivity of definitions is perfectly compatible with the objectivity of the subject that the words are used in.

Ask any astronomer.