The Use and Abuse of Occam’s Razor: On Multiplying Entities Beyond Necessity

Self-styled neo-Aristotelian Richard Hennessey's response to my three posts concerning his theory of accidental predication is now online. 

He graciously declines my suggestion that he make use of accidental compounds or accidental unities in his theory despite the excellent Aristotelian pedigree of these items, a pedigree amply documented in the writings of Frank Lewis and Gareth Mathews.  Following Mathews, I characterized accidental compounds as 'kooky' objects with as little pejorative intent as I found in Mathews who defends these items. Hennessey, however, apparently takes the label pejoratively:

I cannot help but agree that the seated-Socrates in question, as a being other than Socrates, is a “‘kooky’ or ‘queer’ object.” And I cannot help but wonder how anyone who rejects universals could be tempted to multiply entities and accept such a “‘kooky’ or ‘queer’ object.”

So before examing the meat of Hennessey's response to me, in a later post, we must first tackle some preliminary matters including the nature of Occam's Razor, its use and abuse, and the role of explanation and explanatory posits in philosophy.

On Brandishing the Razor

I am not historian enough to pronounce upon the relation of what is standardly called Occam's Razor to the writings of the 14th century William of Ockham. The different spellings of his name will serve as a reminder to be careful about reading contemporary concerns into the works of philosophers long dead. Setting aside historical concerns, Occam's Razor is standardly taken to be a principle of theoretical economy or  parsimony that states:

   OR. Do not multiply entities beyond necessity.

It is sometimes formulated in Latin: Entia non sunt multiplicanda praeter necessitatem. The principle is presumably to be interpreted qualitatively rather than quantitatively, thus:

   OR*. Do not multiply TYPES of entity beyond necessity.

Thus it is not individual entities that are not to be multiplied, but types or kinds or categories of entity.  To illustrate.  Some criticized David Lewis' extreme modal realism on the ground that it proliferates concreta: there are not only all the actual  concreta , there are all those merely possible ones as well.  He responded quite plausibly to the proliferation charge by pointing out that the Razor applies to categories of entity, not individual entities, and that category-wise his ontology is sparse indeed.

'Multiply' is a picturesque way of saying posit. (Obviously, there are as many categories of entity as there are, and one cannot cause them to 'multiply.')  And let's not forget the crucial qualification: beyond necessity.  That means: beyond what is needed for purposes of adequate explanation of the data that are to be explained.  Hence:

OR**  Do not posit types of entity in excess of what is needed for purposes of explanation.

So the principle enjoins us to refrain from positing more types of entity than we need to explain the phenomena that need to be explained. It is obvious that (OR**) does not tell us to prefer theory T1 over theory T2 if T1 posits fewer types of entity than T2. What it tells us is to prefer T1 over T2 if T1 posits fewer types of entity AND accounts adequately for all  the data. So there is a trade-off between positing and accounting.

Our old pal Ed over at Beyond Necessity often seems to be unaware of this.  He seems to think that simply brandishing the Razor suffices to refute a theory.  Together with this he sometimes displays a tendency to think that whole categories of entity can be as it were  shamed out of existence by labeling them 'queer.'  I picked up that word from him.  A nice, arch, donnish epithet.  But that is just name-calling, a shabby tactic best left to the ideologues. 

Hennessey is perhaps not guilty of any name-calling or entity-shaming but I note that he too seems to think that merely waving the Razor about suffices as a technique of refutation. One piece of evidence is the quotation above where he states in effect that to posit accidental compounds such as seated-Socrates is to multiply entities.  But this is to ignore the crucial question whether there is any need for the positing. 

What is offensive about Razor brandishing is the apparent ignorance on the part of some brandishers of the fact that we all agree that one ought not posit types of entity in excess of the needs of explanation. What we don't agree on, however, is whether or not a given class of entities is needed for explanatory purposes.  That is where the interesting questions and the real disagreements lie. 

Hennessey eschews universals in the theory of predication, and elsewhere.  Fine.  But he cannot justify that eschewal solely on the basis of Occam's Razor which is a purely methodological principle.  In other words, the Razor does not dictate any particular ontology.  Taken as such, and apart from its association with the nominalist Ockham, it does not favor nominalism (the view that everything is a particular) over realism (the view that there are both particulars and universals).  It does not favor any ontology over any other. 

Nor does it rule out so-called 'abstract objects' such as Fregean propositions.  I gave an argument a while back (1 August 2010 to be precise) to the conclusion that there cannot, as a matter of metaphysical necessity, be nothing at all, that there must be at least one abstract object, a proposition.  Hennessey commented on that post, Thinking about Nothing, and made the objection that I was multipying entities.  But again, the salient question is whether the entity-positing is necessary for explanatory purposes.  If my argument was a good one, then it was.  One cannot refute such an argument simply by claiming that it introduces a type of entity that is less familiar than one's favorite types.

To sum up.  Philosophy is in large part, though not entirely, an explanatory enterprise.  As such it ought to proceed according to the methodological principle formulated above as (OR**).  This principle is not controversial.  Hence it should not be presented to one's opponents as if it were controversial and denied by them.  Nor is it a principle that takes sides on the substantive questions of ontology.  Thus the following argument which is suggested by Hennessey's remarks is invalid:

1. OR**
2. Accidental compounds are a category of particular distinct from both substances and accidents.
Ergo
3. There are no accidental compounds. 

Non sequitur!  He needs a premise to the effect that the positing of accidental compounds is otiose since the explanatory job can be adequately done without them.  He needs such a premise, and of course he needs to defend it.

What I am objecting to is the idea is that by earnest asseverations of a wholly uncontroversial methodological principle one actually  advances the substantive debate.