Logic Flashcards
What is logic
The study of whether one argument supports or provides reason to believe another
Descriptive Claims
How the world is, things we can observe
Normative Claims
Things that ought to be true, what the world should be like
Prudence
To be cautious, careful, or wise about a situation
Bridge Principles
Tells you what descriptive facts must be established in order to support a
particular normative claim
Deductive Logic
Uncommon; reasoning that is so strong, that if the premises are true, the
conclusion must be true
Inductive Logic
More common; reasoning that provides some evidence for our conclusions
but could be overridden
Conditional Arguments
A Type of Deductive Argument that starts by saying IF one thing is true, THEN another must be true
Necessary Conditions
“In order to get paid, I have to go to work”
Sufficient Conditions
“If I meet all my sales goals, I will get at least a 5% bonus”
Necessary But Not Sufficient
“Wearing a suit is necessary to impress the boss, but
you need to do good work too”
Sufficient But Not Necessary
“If I take the subway, I will arrive at Yonge-Dundas”
Necessary And Jointly Sufficient
“If I wear a suit and tie, bring my invitation, and
arrive on time, I will be allowed in for dinner”
Deductive Conditional Arguments (MP and MT)
Arguments that have an “If…, then…” claim as
an important premise
Modus Ponens
“If A, then B. A. Therefore B.”
Modus Tollens
“If A, then B. Not B. Therefore Not A.”
Affirming the Consequent
“If A, then B. B. Therefore A.”
Denying the Antecedent
“If A, then B. Not A. Therefore Not B.”
Inductive Logic & Reasoning
When we have some evidence for our conclusions but that
evidence could be overridden
Generalizations
Start with a number of observed instances (a “sample”) and reason to a conclusion about an extension of the pattern to a larger class of things (the “population.”)
Simple Induction
“Proportion X of group G has characteristic C. Individual I is a member of G.
The probability that I has C is X” (formula for evaluating simple induction)
Inference to Best Explanation
The things we observe often leave us needing to determine the cause behind them, and in many situations we can often name many possible causes (believe the one that offers the best explanation)
The BEST acronym
BACKGROUND KNOWLEDGE; EXPLANATORY
POWER; SIMPLE; TESTABALE
Argument By Analogy
Arguments that take the form of a comparison
Ethical Versus Prudent Claims
● Descriptive Claims = Physical Facts
● Normative Claims = Ethical or Prudent
Normative Claims alone can _____ support a descriptive conclusion
never
Descriptive Claims alone can ______ support a normative conclusion
never
Premises need to be ________ rather than true
acceptable
Deductive arguements
Provides an airtight link between premises and conclusion. If the premises are true and the logic is good, the conclusion must also be true
Inductive arguements
Provide examples, or bits of evidence, in favor of a conclusion. But even if the premises are true and the logic is strong, it’s still possible that the conclusion is false
