A statement should be self-consistent both in its expression and the
assertion it conveys
This is a version of a very fundamental logical principle first stated
by Aristotle. It is sometimes called, somewhat confusingly, the 'law
of contradiction' and is expressed in various ways. For example, one
version runs 'a class of entities cannot both have a certain property
and not have it' or more abstractly: 'A cannot be both B and not-B'.
A case of these versions would be, for example, 'A guitar cannot be
both a stringed instrument and not a stringed instrument'. Whether this
law of contradiction holds true for absolutely all individual things
or all classes of entity is problematical and belongs more to the sphere
of logic and ontology than semantics, though these are frequently interrelated.
In the above formulation as the principle of non-contradiction the accent
lies on language and the assertions made by it rather than on ontological
or scientific questions as to the nature of actual things and events.
As a principle in semantics it sets a norm for clear thinking and expression
rather than expressing any law about the nature of things. The aim is
to remove the self-contradictory use of terms and the concepts they
express.
More explicitly, the principle of non-contradiction is broken in the
following typical cases:-
Case 1) Where the same term is used twice in opposite senses
Eg) 'The colour white is not a colour'. This is a case of circularity
of meaning or of a 'vicious circle in thought'. The tern 'colour' is
used in two incompatible senses, for white cannot be both a colour and
not a colour. We might assume that the intended assertion was badly
expressed and would have been self-consistent in the expression "White
is not a colour". Though white is often regarded as and called
a colour in ordinary usage or in Goethe's theory of colour, Newton's
theory requires that white is the neutral, uncoloured quality of light,
the refraction of which alone produces colours. We are not here concerned
with the ontological or scientific question of what whiteness itself
is, only with being consistent in the use of the term 'white'.
Obviously the same term can be used in opposite senses in different
expressions, such as in different chapters of a book. This would extend
the principle beyond its present formulation. It would be valid and
useful in application if extended to the case of any two or more statements
because it is in long texts that it is most likely to be broken and
go unnoticed.
Case 2) Where the logical predicate of the assertion expressed contradicts
the logical subject
Eg) "We know for certain that nothing can be known for certain."
Let us presume that the terms 'know' and 'certain' have the same sense
in the example, then the assertion itself is absurd. The logical subject
'We know for certain' is contradicted by the logical predicate 'that
nothing can be known for certain' because the term 'nothing' excludes
the possibility of knowing anything for certain. Since this leads thought
into a vicious circle, it cannot effectively communicate any meaningful
assertion. This indicates the relevance of this principle to semantics.
Eg. "Sixty-five plus twenty-one equals ninety-six".
According to the axioms of mathematical usage of numerical terms, this
is a contradiction. The assertion expressed is not clearly conceivable
to the mind, so we reject it as an error, whether as one of calculation
(conceptual confusion) or of a misuse of terms.
With this last example in mind we see that the principle
aims at ensuring that assertions are made clearly conceivable as a prerequisite
of efficient communication. Care should be taken in analysing for suspected
breaks of the principle because apparent contradictions may prove solvable
on closer inspection. For example, "Let us assume that humans cannot
attain certain knowledge" is not contradictory because 'Let us
assume that' makes the statement conditional, not a categorical assertion
of the truth.
Case 3) Where a term or expression is used in a way that contradicts
common usage, without making clear that it is to be used in this uncommon
way.
Eg) "What is totally impossible can only be achieved by aiming
to do what is impossible".
The common usage of the term totally impossible' is quite categorical
and a directly contrary term to 'possible'. 'Impossible' commonly includes
'that which cannot be achieved'. The above example therefore expresses
a self-contradictory assertion.
2) Analyse the following advertisement texts to decide whether each
one is self-contradictory or not, giving reasons:-
"Munchables are simply the best, while our new Super-munchables
are even better."
"You can't go wrong with our latest Cursill washing powder, and
if you do then there's Extra Cursill, which any fool can use properly."
3) Decide whether the following expression is contradictory or not,
explaining upon what you base your decision:-
"The balance of power that all agree presently exists between the
Warsaw Pact countries and those of N.A.T.O. depends entirely upon the
maintenance of the U.S.A.'s military superiority over the U.S.S.R."
4) EO "Nothing is ever created or destroyed, for what exists in
creation always arises from or is destroyed by some creator."
a) Consider whether contradiction arises in the above expression and,
if so, whether you judge it to be the result of inconsistent use
5) Consider the following exchange of views:-
A: The advance of micro-computer technology will result in less employment.
B: Yes. It can result in shorter working hours for all.
A: But it will also result in fewer jobs than will be needed.
B: I don't necessarily agree, for that depends entirely upon how it
is introduced into economic life.
a) State clearly A's and B's interpretations of the term 'less employment'
in A's first expression.
b) Evaluate whether these interpretations are more-precise than the,
term 'less employment', giving grounds,
c) Does pseudo-agreement occur in the above discussion? Give grounds.