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					Arguments and Their
    Evaluation


   Basic Definitions
Arguments (Pieces of Reasoning)
 An argument is...
Arguments (Pieces of Reasoning)
 An argument is a set of statements...
Arguments (Pieces of Reasoning)
 An argument is a set of statements one of
 which is being argued for on the basis of
 the others
Arguments (Pieces of Reasoning)
 An argument is a set of statements one of
 which is being argued for on the basis of
 the others
 Given this, the statements other than the
 statement that’s being argued for can be
 described as...
Arguments (Pieces of Reasoning)
 An argument is a set of statements one of
 which is being argued for on the basis of
 the others
 Given this, the statements other than the
 statement that’s being argued for can be
 described as the statements in the argument
 that are being argued from
Arguing For and Arguing From
 Arguing for a statement isn’t just making it
 or endorsing it publicly; rather, arguing for
 a statement is...
Arguing For and Arguing From
 Arguing for a statement isn’t just making it
 or endorsing it publicly; rather, arguing for
 a statement is giving reasons for thinking
 that it’s true
Arguing For and Arguing From
 Arguing for a statement isn’t just making it
 or endorsing it publicly; rather, arguing for
 a statement is giving reasons for thinking
 that it’s true
 Similarly, arguing from one or more
 statements is...
Arguing For and Arguing From
 Arguing for a statement isn’t just making it
 or endorsing it publicly; rather, arguing for
 a statement is giving reasons for thinking
 that it’s true
 Similarly, arguing from one or more
 statements is giving them as reasons for
 thinking that the statement that is being
 argued for is true
Premises and Conclusions
 The premises of an argument are...
Premises and Conclusions
 The premises of an argument are the
 statements that are being argued from
Premises and Conclusions
 The premises of an argument are the
 statements that are being argued from
 The conclusion of an argument is...
Premises and Conclusions
 The premises of an argument are the
 statements that are being argued from
 The conclusion of an argument is the
 statement that’s being argued for
Premises and Conclusions
 The premises of an argument are the
 statements that are being argued from
 The conclusion of an argument is the
 statement that’s being argued for
 Note: these definitions imply that strictly,
 there can be only one conclusion in any
 given argument.
Possible Sources of Misunderstanding
 The words “argument,” “premise,” and
 “conclusion” all have other meanings
 Often, when arguments are presented, parts
 are left unstated (as in enthymemes)
 Arguments in an extended sense of the term
 (e.g. chain arguments, reductio arguments,
 and conditional proofs) can be much more
 complex than any of this suggests
Arguments and Their
    Evaluation

    Definitions of
   Evaluative Terms
Lousy Arguments
 A lousy (or crummy) argument is an
 argument that is such that even if its
 premises are true...
Lousy Arguments
 A lousy (or crummy) argument is an
 argument that is such that even if its
 premises are true, its conclusion is no more
 likely to be true than false
Inductive Arguments
 An inductive argument (or an argument of
 at least some inductive strength) is an
 argument that is such that if its premises are
 true, then...
Inductive Arguments
 An inductive argument (or an argument of
 at least some inductive strength) is an
 argument that is such that if its premises are
 true, then its conclusion is more likely to be
 true than false, although it could, at least
 conceivably, be false even if all the
 premises are true
Valid Arguments
 A valid argument is an argument that is
 such that if its premises are all true, then...
Valid Arguments
 A valid argument is an argument that is
 such that if its premises are all true, then its
 conclusion has to be true—can’t be false
Valid Arguments
 A valid argument is an argument that is
 such that if its premises are true, its
 conclusion has to be true—can’t be false
 Note: the conclusion of a valid argument is
 said to be entailed by the premises, or to
 follow from them, or to be deducible from
 them, or to be a logical consequence of
 them
Sound Arguments
 A sound argument is...
Sound Arguments
 A sound argument is a valid argument all of
 the premises of which are true
Sound Arguments
 A sound argument is a valid argument all of
 the premises of which are true
 Note: one of the implications of this
 definition is that a sound argument cannot
 have a false conclusion
Sound Arguments
 A sound argument is a valid argument all of
 the premises of which are true
 Note: one of the implications of this
 definition is that a sound argument cannot
 have a false conclusion
 Note: another is that there can be sound
 arguments no one knows to be sound
Good Arguments
in the Strict Sense of the Term
 An argument is a good argument in the strict sense
 of the term just in case it is either:
    a strong inductive argument with true premises or
    a sound argument the conclusion of which isn't
    included among the premises, and the validity of which
    isn't merely a function of its conclusion's being a
    statement that couldn't conceivably be false
 NB: the phrase “good argument” has other senses
 too; valid arguments are sometimes called “good”
 just because the reasoning in them is good.
Rationally Compelling Arguments
 A rationally compelling argument is a
 good argument in the strict sense of the
 term that meets these additional conditions:
   all its premises are known to be true, and
   no equally good argument for the falsity of the
   conclusion is known to exist
 Note: clearly, rational compellingness is a
 relative thing, even if truth is not
Rhetorically Effective Arguments
 Last but not least, a rhetorically effective
 argument is...
Rhetorically Effective Arguments
 Last but not least, a rhetorically effective
 argument is an argument that typically
 succeeds in persuading those to whom it is
 presented of the truth of its conclusion—
 whether or not it is unsound, invalid, or
 even utterly lousy from a logical point of
 view

				
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