Truth Tests
Correspondence, Coherence, Pragmatic
(only one “t” in the lot and it’s little)
Sunday, September 15, 13
Correspondence Theory
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A statement is true if it corresponds to a fact
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Problems: Our knowledge of the world is
mediated through (potentially fallible) perception
and language (we have no access to the thing
itself); not all knowledge claims relate to facts (the
painting is beautiful)
Sunday, September 15, 13
Examples: Tracy High School is located at 315 east
11th street, All mammals nurse their young, There
are two sheep in the field
Coherence theory
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A statement is true if it coheres, or is consistent
with, an established body, or system, of knowledge
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Examples: There are an infinite number of primes,
the speed of light, The sum of the interior angles of
a triangle equals 180 degrees
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Problems: Coherence theory is system
dependent, if the system is flawed, any truth
derived from that system is flawed (note: truths
derived from flawed systems may still correspond
to observable facts)
•
How does this theory of truth relate to Gladwell?
Sunday, September 15, 13
Problems with Coherence theory example 1 - the geocentric universe
Clip from Universe: the Infinite Frontier, PBS, 1994
Sunday, September 15, 13
Problems with coherence theory Example II - Euclid’s triangles
Given the system established by
Euclid’s axioms that it is
possible:
• To draw a straight line from any point to any
point.
• To produce a finite straight line continuously
in a straight line.
• To describe a circle with any center and
distance.
It is possible to demonstrate that the
sum of the interior angles of any
triangle equals 180 degrees because
this coheres to the system established
by Euclid’s axioms
and,
• That all right angles are equal to one another.
• There is just one straight line through a given
point which is parallel to a given line
Sunday, September 15, 13
x + y + z = 180
. . . but in the 19th century, G.F.B. Riemann (and
others) demonstrated that this was not always true
when he demonstrated that the internal angles of a
triangle drawn on the surface of a sphere always have a
sum greater than 180 degrees
Again, the key here is that a truth
demonstrated through coherence
theory is sensitive to the limitations
of the system to which it coheres.
Sunday, September 15, 13
Pragmatic Theory
•
•
A statement is true if it is useful
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Problems: If a and b always occur together, we
can’t say a causes b (correlation is not causation),
pragmatic theory leads to circular reasoning (truth
justified by usefulness and usefulness justified by
truth)
Sunday, September 15, 13
Examples: Belief that God exists helped John
beat alcoholism, therefore God exists
Limitations with theories of truth lead
some to two extreme positions
•
Relativism - truth is always dependent on
perspective (more on this when we discuss ethics
next year)
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Skepticism - There is no truth (that we can know)
Sunday, September 15, 13
Questions for the skepticism reading
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What is the difference between “ordinary” and “philosophical” skepticism?
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How are the movies The Matrix and The Truman Show used to illustrate the
difference between ordinary and philosophical skepticism?
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What knowledge questions are raised by this article?
Sunday, September 15, 13
What does Wittgenstein mean when he says “doubt occurs within the
context of things undoubted?” Is he speaking of ordinary or philosophical
skepticism with this statement?
Are you a philosophical skeptic? Explain your answer.