Transcript Informal Logic, Famous Fallacies

3 Theories of Truth:
Pragmatic
Coherence
Truth is what works, or serves
our purposes
Truth is what coheres with the
rest of our knowledge
Correspondence
Truth is what corresponds to facts
The Coherence Theory:
 seems circular or question begging: it defines
truth in terms of coherence with our knowledge.
But knowledge presupposes true belief.
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If we know something, then surely anything that
contradicts that knowledge will be false. But how
do we get knowledge in the first place?
What if we only knew one thing?
The Pragmatic Theory:
 seems compatible with many things we think
are false
 belief in spirits or ghosts may work or serve
the purposes of mediums and fortune tellers
… we still want to say those beliefs are or may
be false
The Correspondence Theory
 seems to be what we mean when we say
something is true
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My pancake is salty! (we seem to agree that
someone told the truth when we check the
pancake and find it salty)
Coherence and Pragmatic theories seem to
confuse a test of truth with what constitutes it
If truth is correspondence (not all philosophers accept
this), what are the terms of the correspondence?
One candidate pairing is a sentence and a fact, but since
‘Puellam amo’ and ‘I love the girl’ are different
sentences, but say the same thing, it’s better to have a
name for what a sentence says than to make those
different sentences the bearer of one truth.
Philosophers call what a sentence says a proposition.
So truth is correspondence b/w propositions and facts.
But what are facts?
The best way to think of a fact is as a state of affairs.
Imagine a ruler on a desk. That is one state of affairs.
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Another is the distance of the ruler from one of the corners
Another is the distance to another corner, and yet another
Another state of affairs is the color of the ruler
Another, the color or the desk.
You see where this is going…
So, from the previous example, the world is composed of
innumerable, though perhaps not infinite, states of
affairs, or facts.
“The world is the totality of facts, not of things.” -Ludwig
Wittgenstein
Sentences, or propositions, express facts we select from
the world.
Experience teaches us to be selective about which facts
we seek to express.
From this account we see that it is confusion to
speak of “true facts.” Or, for that matter, false
facts.
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Facts just are.
Facts are the target.
We don’t say the target was true; we say the
archer’s aim was true.
When truth does occur, it will be the proposition
which is true, not the fact, and the proposition
will be true only because of the fact.
‘Snow is white’ is true if and only if snow is
white. –(Alfred Tarski, Polish logician)
What that means is, the sentence is true if and
only if it corresponds to a fact.
Breaking it down (analyzing it, somewhat sloppily):
‘Snow is white’ is true if and only if
 there is an entity referred to by the term ‘snow’
 there is an entity referred to by the term ‘white’
 there is an exemplification relation referred to by the term
‘is’, such that,
 the entity referred to by the term ‘snow’ has the property
referred to by the term ‘white’, and
 the having of the property is expressed by the use of the
term ‘is’
Notice, this analysis will have problems accounting for the
truth of statements about the future, fictional beings, and
the whole theory may have other problems. See
http://plato.stanford.edu/entries/truth-correspondence/#5
One last word about facts: notice that facts, as
such, indicate nothing about how well or poorly
we know them. There are gazillions of unknown
facts.
In journalism school, students are taught to use the
term ‘fact’ only for
 what can be known by the reader’s reflection
(like 2+2=4), or
 what can be easily inspected (Abe Lincoln was
president)
So, how should we understand this
disagreement?
Evolution is a fact, not a theory!
or
Evolution is a theory, not a fact!
What is a theory, anyway?
A theory is one possible explanation among other possible
explanations
Theories are competing explanations
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That doesn’t mean there must be two or more actual
explanations competing before we can call one or the other
a theory
It does mean we use the term theory when we recognize
the door is open to possible competing explanations
(otherwise, we call our explanation the explanation, not a
theory)
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Consider the “you or the dog ate the cookie case.”
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If that's a good definition, that makes every
explanation a theory
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relative to level of skepticism, or
relative to ability to conceive of alternative
explanations
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Consider debate over 2+2=4.
Consider the previous definition to any of the 6
you will read in Merriam Webster’s dictionary
http://www.merriam-webster.com/dictionary/theory
Compare the previous definition to The National
Academy of Sciences’ definition of theory:
http://nationalacademies.org/evolution/Definitions.html
Aristotle distinguished between real and verbal
definition
Verbal definition = definition of words
Real definition = definition of things
Dictionaries contain verbal definitions, which tell us
what words mean
Scientists and philosophers sometimes seek real
definitions, which tell us what things are
Real definitions try to express that ‘whatness’ or
‘essence’ of a thing
Perhaps the most fundamental distinction of reality
is between existence and essence:
Existence: that something is
Essence: what something is
In answering the question what something is, we
are providing a real definition
Genus – Difference Definitions (also mistakenly called
Genus – Species definitions)
A Genus is a group or kind of thing
A Species is a subgroup of that group or kind
Genus and Species are relative terms:
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a genus may be a species of some other larger group
a species may be a genus if it contains yet smaller groups
Example of relative classification terms:
Life form (genus)
Animal (species)
Animal (genus)
Mammal (species)
Mammal (genus)
Tiger (species)
Tiger (genus)
Bengal tiger (species)
Biologists have more rigid taxonomy where genus
and species are used in a non-relative way:
Kingdom, phylum, class, order …
In a genus – difference definition,
 the “species” are separated from one another
by the “difference,” or, you might say,
 the difference is an attribute or attributes that
distinguish species from one another
Daughter = offspring, female
Species
Genus
Difference
Biography = book, on a person
Species
Genus
Difference
Skyscraper = building, very tall
Species
Genus
Difference
Consider 2 definitions of human being:
1. Featherless biped
2. Rational animal
Both are genus – difference, or genus – specific
difference definitions of the species ‘human’
or ‘human being’
Consider 2 definitions of human being:
1.
Featherless biped
2.
Rational animal
Which definition is better?
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In terms of uniqueness? (too broad or narrow?)
In terms of expression of whatness or essence?
In addition to Genus – Difference definitions, there
are:
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Ostensive: defining a term by pointing
Enumerative: by naming members of the class the term
refers to
Subclass: by naming subclasses of the class the term
refers to
Synonymous: by identifying a term with a synonym
Etymological: by citing the term’s origin
Operational: by using a test that tells whether a term
applies to a thing