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202 STRÖSSNER
this is relevant, then A must say so” (McCarthy 1986: 91). McCarthy emphasizes that such
conversational rule “Assume S are P” doesn’t presuppose any statistical facts about S and P.
Statistical information cannot falsify a rule. Applied to normality statements this reflection
yields another non-statistical normality interpretation, a conventional understanding. 3
Conversational Interpretation of Normality
The sentence “S is normally P” is true iff it is assumed that any S is P as long as nothing
else is mentioned.
Though it employs no reference to statistics this interpretation explains the expectations
which can arise from normality assumption in a communication situation where all parties
follow the same rules. Moreover this interpretation subsumes typicality interpretations.
Stereotypes and prototypes, which are by definition commonly known in the community, will
heavily influence our assumptions on what needs to be said explicitly and on what is
suggested implicitly. This interpretation is also able to account for the fact that many
normality assumptions are related to statistical majorities without postulating a relation.
Assuming a rule which applies in many cases is prima facie more efficient than any other
rule.
The conventional reading is the most adequate interpretation of normality from the nonstatistical
viewpoint. Nevertheless there are two serious objections against such a position
which are deeply related to each other. First of all, normality statements, taken as
conventions or typicality statements, are nearly trivial. Anybody who is a linguistically
competent member of the community should know about prototypes, stereotypes as well as
implicit communication rules. Only when you acquire the semantics and pragmatics of a
language such normality statements are truly informative. This feature of the above normality
interpretations is connected to another peculiarity, namely the non-descriptiveness of such
normality readings. Understanding “Normally S are P” in these ways means to deny that such
sentence is really about S. It is our language, i.e. our concepts and way of communication,
that is expressed in this statement. Such conclusion might be acceptable in some cases but is
counterintuitive as a general hypothesis on normality. There are a lot of normality
statements, for example in biological science, which tell something about the nature of the
subject term. A conventional or typicality account of normality cannot account for such
statements.
2.3 Descriptive Normality
There are admittedly descriptive approaches to normality which deny a strong logical relation
to statistical statements. For example, Michael Thompson’s (2008) characterization of
natural-historical judgments indicates that these statements are normality statements but he
strongly rejects that they involve majorities: ‟A natural-historical judgment may be true
though individuals falling under both the subject and predicate concepts are as rare as one
likes, statistically speaking” (Thompson 2008: 68). He understands these judgments
essentially categorical and irreducible to any statement about individuals.
A somehow similar argumentation within the philosophy of biology is found in (Wachbroit
1994). Wachbroit claims that there is an indigenous biological concept of normality which is
distinct from statistical normality. According to him a sentence about a normal biological
3
Note that these communication rules are indeed conventions as defined by Lewis in his famous
“Convention” (Lewis 1969). For the usage of default rules it holds that there is a common interest in
conforming to the same rules. Assuming the same default will allow for a more efficient communication,
while assuming different rules will lead to misinformation and confusion. A default which is sustained
by large majorities is indeed better than a default which rarely applies but even a commonly used rule
which is not related to statistical majorities is much better than non-conformity.