How to Win Every Argument: The Use and Abuse of Logic (2006)

34 How to Win Every Argument

of concealed quantification occurs when ambiguity of expression
permits a misunderstanding of the quantity which is spoken of.

Garage mechanics are crooks.

(What, all of them? It does not say, but there is a big difference. If it

refers to all of them, then to talk to one is to talk to a crook. Although

many motorists may have their convictions, few of the garage

mechanics do.)

Very often the quantification is concealed because it sounds
rather lame to make bold statements about some of a class. 'All' is
much better, but probably untrue. Rather than be limited by
such a technicality, a speaker will often leave out the quantity in
the hope that 'all' will be understood. Someone might com-
miserate with a distraught parent by telling them: 'Teenagers are
troublesome.' This can be accepted as 'some are,' or even 'many
tend to be so', but it could also be taken to mean that one has
only to find a teenager to locate a troublesome person. This may
not have been intended, however plausible it sounds. The fallacy
comes with the ambiguity. The statement can be accepted with
one meaning, yet intended with another. Of course, very dif-
ferent conclusions can be drawn from the two meanings.

It is well known that members of the Campaign for Nuclear Disarma-

ment are communists.

(It is indeed, but not all of them, as seems to be implied. Even if some

are communists, there is still room for others motivated by sincerity

or stupidity.)

The fallacy is widely used to condemn whole groups on the
basis of some of their members.

Subversives teach at the Open University.