Introductory Logic: The Fundamentals of Thinking Well Flashcards
Learn Introductory Logic Terms for Challenge B in Classical Conversations.
Logic
the science and art of reasoning well
Law of Identity
If a statement is true, then it is true.
Law of Excluded Middle
Any statement is either true or false.
Law of Non-contradiction
A statement cannot be both true and false.
Formal Logic
branch of logic which deals with
the proper modes of reasoning
Informal Logic
branch of logic which deals with
operations of thinking that are
indirectly related to reasoning
Induction
reasoning with probability from
examples or experience to general rules
Deduction
reasoning with certainty from
premises to conclusions
Categorical Logic
connects one category (or term) with another
uses syllogisms
Propositional Logic
connects entire propositions together in arguments
term
a concept that can be expressed precisely.
definition
a statement that gives the meaning of a term.
6 purposes of definitions
- show relationships
- remove ambiguity
- reduce vagueness
- increase vocabulary
- explain concepts theoretically
- influence attitudes
ambiguous word
word with more than one meaning.
lexical definition
definition which shows relationships or
reduces ambiguity by providing
a single, established meaning of a term
(dictionary definition)
vague word
word whose extent is unclear.
precising definition
definition which makes more precise
what was vague or fuzzy
(applies only to the situation in which it is used)
stipulative definition
definition needed when a new word is invented
or an existing word is applied in a new way
theoretical definition
definition given for a term, not when the word is unfamiliar, but when the term is not understood
(often scientific or philosophical in nature)
persuasive definition
definition that aims at persuading the listener one way or another toward the term being defined
genus
a term that is more general, broad, or abstract
than the original term and includes it
species
term that is more specific, narrow, or concrete
than the original term and is included by it
(a type, kind or example of the term)
mutually exclusive
not overlapping
exhaustive
complete, no other types exist
3 basic errors to avoid
in genus-species charts
- overlapping species (by changing the dividing principle or by placing a term at the wrong level)
- changing definitions for an ambiguous term
- using parts of the term (should be kinds)
extension
the sum of all the individual obects
described by a term
(how broad is the term?)
intension
the sum of all the common attributes
denoted by the term
(how specific is the term?)
3 methods of defining terms
- synonym
- example
- genus-difference
defining by synonym
giving another word with the same meaning
(problem if the meaning of the synonym is not known
or if no synonym exists)
defining by example
demonstrating the term; giving several and various examples; listing species of the term
(problem because of ambiguity of this method)
defining by genus and difference
naming the genus and then adding descriptive words which distinguish that term from all other species under that genus (OR what group is it in? what makes it different from everything else in the group?)
6 rules for defining by
genus and difference
- state essential attributes
- should not be circular
- should not be too broad or narrow
- should not be unclear or figurative
- state positively if possible
- be the same part of speech as the term
statement
a sentence which is either true or false.
3 types of sentences
that are not statements
- question
- command
- nonsense
self-supporting statements
a statement whose truth value can be determined
from the statement itself
3 types of self-supporting statements
- self-reports
- true or false by logical structure
- true of false by definition
self-report
a statement by a person concerning his own
desires, beliefs or feelings.
true or false by
logical structure
a statement which can be seen to be true or false
by how the sentence is put together
tautology
a statement which is always true
because of its logical structure
(e.g., Jesus is God OR Jesus is not God.)
A or ~A
self-contradiction
a statement which is always false
because of its logical structure
(e.g., Jesus is God AND Jesus is not God)
A and ~A
true or false by
definition
a statement which is necessarily true or false
becaue of the definitions of the words in the sentence
supported statement
a statement whose truth value depends on
evidence or information from outside itself
3 ways to determine the truth value
of supported statements
- authority
- experience
- deduction
authority
a trustworth, authoritative source
e.g., scripture, encyclopedia
experience
trusting our own senses to determine truth value
deduction
reasoning to some conclusion based on
other statements, whose truth value we know
4 relationships between statements
- consistency/inconsistency
- implication
- logical equivalence
- independence
consistency
consistent
when 2 statements can both be true
at the same time
inconsistency
inconsistent
when there is a conflict between 2 statements
so they cannot both be true at the same time
implication
when the truth of 1 statement requires
the truth of the other.
logical equivalence
when 2 statements imply each other
the statements must both be true or both be false
independence
when the truth or falsity of 1 statement
has no effect on the truth or falsity of the other
3 kinds of disagreements
- real
- apparent
- verbal
real disagreement
an actual inconsistency between 2 statements;
they cannot both be true at the same time
(e.g.: Jesus is God. Jesus is not God.)
apparent disagreement
a difference of opinion or perception
(e.g., Ann: I think logic is easy;
Bob: I think logic is hard)
verbal disagreement
a missunderstanding due to differing definitions
for one or more words
the ONE basic verb
in Categorical Logic
(list all forms)
the BEING (to be) verb
am was be
is were being
are been