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What is a set (or class)?

  • a collection of “individuals” having a certain trait, property, or attribute.


What does it mean to have consistent statements?

  • the logical relation between a set of statements that may all be true at the same time

  • “Is it possible for each statement in the set to be true at the same time?”

    • Water is H2O.

    • Water is not H2O.

      • inconsistent set of statements


What makes some sets arguments and others nonarguments? (conceptual analysis):

A set of statements is an argument if and only if

  1. there are two or more statements in the set, and
  2. at least one statement is offered as evidence for the truth of another


What are the two conditions of arguments?

  1. every argument consists of exactly two subsets of statements:

    • evidence (premises)

    • claim (conclusion)

  2. every attempt to show that a claim is true on the basis of its evidence is an attempt to show that the truth of the claim follows from the truth of its evidence.

    • deduction or inference


What does it mean to have deductive statements?

  • the logical relation between statements occurring whenever one statement is concluded to be true on the basis of another


What are conclusion indicators?

  • certain words and phrases that reliably (but not always) indicate the presence of an argument’s conclusion


What are some conclusion indicators?


What are premise indicators?

  • certain words and phrases that reliably (but not always) indicate the presence of a premise


What are some premise indicators?


What is a standard form (for arguments)?

  • a list of statements separated by a line. The numbered statements above the line are always the premises.

  • The conclusion will always be the single statement written below the line to the right of the symbol ‘∴‘ (which is read “therefore”)


What is to read actively?

  • physically marking up a passage while you are reading it in order to reveal the logical structure of the argument it asserts
    • identify conclusion indicator and conclusion
    • identify premise indicators and premises, and number them.
    • Write the argument in standard form.


Useful generalizations of arguments

  1. An argument has exactly one conclusion and it may occur anywhere within a passage.
  2. Every argument can be expressed in the form of a single conditional declarative sentence.
  3. A statement is a premise or a conclusion only in relation to other statements within a particular argument.
  4. Every premise is an (explicit or implicit) assumption.
  5. Some conclusions are implied rather than stated explicitly.
  6. Not every statement in a passage needs to be either a premise or the conclusion.
  7. A passage may contain more than one argument.


What is an assumption?

  • a statement whose truth is presupposed but not shown

    • explicit assumption= an assumption that is “out in the open” for everyone too see or to hear

    • implicit assumption= something “hidden” behind what is written or said.


What is a presupposition?

  • an implicit assumption

    • No one can reasonably make an assertion without implicitly assuming (presupposing) certain basic things about the world.

    • No one can reasonably ask a question without implicitly assuming (presupposing) certain things about the world and the individual being asked the question (command or request).

  • sometimes the ability to correctly evaluate an argument relies upon your ability to recognize its implicit presuppositions.


What is an implied premise?

  • that single implicit assumption that mediates between what is assumed explicitly and what is claimed to follow from it; any implicit assumption (presumption) in an argument


What is an enthymeme?

  • an argument with either an implied premise or an implied conclusion


What is a dubious assumption?

  • when the evidence in support of a claim explicitly or implicitly presupposes the truth of something that is both unproven and unreasonable


What is an implied conclusion?

  • an implicit claim

    • if you encounter them, write them on the margin


What is begging the question?

  • the error in reasoning occurring whenever a claim is assumed to be true among the evidence offered to show that the claim is true


What is a rhetorical question?

  • a question posed for effect, not for an answer

    • Never reconstruct an argument with a rhetorical question as either a premise or a conclusion.

    • questions do not have truth-value


What is a nonargument?

  • anything that is not an argument


What is a proof?

  • special kind of argument consisting of assumptions, and a series of deductions


What is the principle of charity?

  • give the arguer the benefit of the doubt whenever possible, and do not assume that he or she is irrational