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PHI 1101 Study Guide - Midterm Guide: Soundness, Principle Of Bivalence, Deductive Reasoning

Course Code
PHI 1101
Laura Byrne
Study Guide

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PHI1101 Definitions
Statement: A sentence used to make a claim. Statements are capable of being either
true or false. (Also called assertions or propositions)
Law of non-contradiction: it is impossible for both a proposition and its negation to
be true at the same time. (One cannot assert both p and ~p at the same time.)
Law of excluded middle (Law of Bivalence): every proposition must either be true or
false. Any middle position between truth and falsity is excluded.
Consistency: A set of propositions is consistent if and only if it is possible for all of
the sentences in that set to be true at the same time.
Inference: a relationship between two thoughts that occurs when one thought
supports, justifies or makes it reasonable to believe another thought.
Argument: a set of statements that claims that one or more of those statements,
called premises, support justify, or make it reasonable to believe that another of
those statements, the conclusion, is true. (exhibits the logical relationship of
Logical strength: an argument has logical strength when the premises, if true,
actually provide support for, justify, or make it reasonable to believe that the
conclusion is true. The premises don’t actually have to be true
Soundness: an argument is sound if it is logically strong and it has true premises.
Inductive arguments: in virtue of its logical form, an inductive argument claims that
the truth of its premises makes the truth of its conclusion probable. (When logically
strong or weak, referred to as inductively strong or inductively weak.
Deductive arguments: In virtue of its logical form, a deductive argument claims that
the truth of its premises guarantees the truth of its conclusion.
Deductive validity: an argument is said to be deductively valid if and only if
whenever all the premises are true, the conclusion must also be true.
Disjunctive Syllogism: a complex proposition that has the form either p or q
Reductio ad Absurdum: one way to show that a proposition is false is to show that a
contradiction follows from it.
Enthymeme: an argument in which the conclusion or one of the premises has been
left unstated.
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