Convention (5) – objections

by Neil Rickert

In this post I’ll respond to some of the objections raised by John Wilkins, as best I understand them.  John raised objections during our discussions in comments to his blog post “Are species theoretical objects“.  I want to be clear that I am not picking on John.  It is my impression that many philosophers have similar views, and I have come across that sort of disagreement in discussions elsewhere.

I’ll start with a quote from that discussion, which I think reasonably summarizes John’s position.

As to conventions, again we may mean different things. I am basing my understanding on a read through of Lewis’ Conventions a while back. Consider correctly driving on the left side. Yes, if we all did the same things we’d all be driving on the left, but there is no fact of the matter which is best, left or right. In the same way, we may all choose to classify using the same conventions, but there need be no fact of the matter tracked in virtue of it being a conventional classification. If all we are doing is following conventions, then the ranks or categories so constructed are flatus vocus. There is nothing “out there” that is being tracked.

A hypothetical

To aid discussion, I want to set up a hypothetical scenario.  The idea is to allow us to thereby avoid getting into biological technicalities.  For this scenario, we shall assume that small animals have been categorized into two groups.  And we shall assume that the categorization is on the basis of conventions.  These two groups or categories will be called “cats” and “dogs”.  I’m using those easy to pronounce names, but we need not assume that I am discussing actual cats and actual dogs.

We assume that biologists have developed a list of criteria, which we shall the “cat criteria”, and that an organism which meets those criteria is then called a cat.  And, similarly, they have developed a “dog criteria” list.  What makes these conventions, is that the criteria have been discussed, with the final criteria lists resulting from a consensus.  As a result of that consensus, biologists have agreed to use those criteria in their classification.

Are the categories real?

The reality of the categories seems to be something that John doubts.  I’m not sure why, because I went through an argument for their reality earlier in the discussion.

Here’s the point.  Anyone who applies those sets of criteria will come out with pretty much the same groupings.  I suggested that if an alien from the Andromeda galaxy were to visit, and apply those criteria, he would come up with the same decisions as to what are cats and what are dogs.  The scientists who established these criteria have tested them for the reliability with which they can be applied.

I’ll note that I suggested an alien from Andromeda, to make the point that the categorization into the two groups is not a matter of purely subjective or purely human judgment.

So it seems to me that the criteria are therefore real, and the division is into groups or categories that are thus also real.  There may be people who disagree, but I really wonder what it is that they mean by “real.”

There is no matter of fact

The question of whether there is a matter of fact was a problem that John raised.

Let’s be specific.  Suppose that I make the statement “A cat is any organism that meets the cat criteria.”  Then, I agree on that technical point.  Looked at as a description of the world, that does not express any matter of fact.  It expresses what Hume would have called “a relation of ideas” rather than a matter of fact.  It is the kind of statement that is said to be analytic, or true by virtue of the meanings of the words used.

The conventions that we are discussing are not mere word-use conventions.  They are behavioral conventions.  The list of cat criteria specifies how we are supposed to decide whether a particular animal is a cat.  With that in mind, let’s look at the statement “people follow the cat criteria in deciding whether a small animal is a cat.”  There is a matter of fact about this.  We have to observe how people categorize, to see if this statement is true.  So it is a posteriori; it is a synthetic statement.  It is also a factual description of how most people will decide if the animal is a cat.  We know that, because that is what it means for these criteria to be part of a social convention.  However, particular instances could be false, as some people might misapply the criteria or might just guess without applying them.  So specific instances of that statement could be false, even though it is generally true.  And that is how we can know that there is a matter of fact.

I look out the window, and announce “There’s a cat in the backyard.  It is a cat, not a dog.”  That sort of statement also expresses a matter of fact.  Being able to categorize into the two groups, cats and dogs, make available a large number of factual statement of this kind.  Without such a categorization, we would only be able to say the less specific “There is a small animal in the backyard.”  So having these conventions has potentially made available to us a large number of factual statement that could not have been expressed without the conventions.  To me, that indicates that the conventions have increased the amount of knowledge available to us.

That the assertion of the conventions themselves are not matters of fact seems of no importance, given the knowledge that has been made available by adopting those conventions.


I see one of the roles of these conventions as being to provide a basis for intentionality.  The word “intentionality”, as used in philosophy, refers to the ability of our words and sentence to be about something.  “Intentionality” is sometimes alternatively called “aboutness”.  For the case of our hypothetical, it is by following our conventions, as expressed in those criteria lists, that we are able to connect the words “cat” and “dog” to specific things in the world.


The objections that have been raised do not seem to apply.  The use of categorization conventions does seem to give us real categories, provided only that the criteria used for those conventions are real (i.e. repeatable and reliable) criteria.  Using those conventions increases the number of factual statements that are potentially available to us.  And the conventions themselves contribute to the meaningfulness or intentionality of the part of our language that is relevant to those conventions.

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