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# Logic: Chapter 1-1.5

### Logic 1.1-1.5

Question | Answer |
---|---|

Logic | The study of the methods and principles used to distinguish correct from incorrect reasoning. |

Proposition | An assertion that something is (or is not)the case; all propositions are either true or false. |

Statement | The meaning of a declarative sentence at a particular time; in logic, the word "statement" is sometimes used instead of "proposition." |

Simple Proposition | A proposition making only one assertion. |

Compound Proposition | A proposition containing two or more simple propositions. |

Disjunctive (Or Alternative) Proposition | A type of compound proposition; if true, at least one of the component propositions must be true. |

Hypothetical (or Conditional) Proposition | A type of compound proposition; it is false only when the antecedent is true and the consequent is false. |

Inference | A process of linking propositions by affirming one proposition on the basis of one or more other propositions. |

Argument | A structured group of propositions, reflecting an inference. |

Premise | A proposition used in an argument to support some other proposition. |

Conclusion | The Proposition in an argument that the other propositions, the premises, support. |

Even when premise and conclusion are united in one sentence, the conclusion of the argument may come first. | Every law is an evil, for every law is an infraction of liberty. |

Deductive Argument | Claims to support its conclusion conclusively; one of the two classes of the argument. |

Inductive Argument | Claims to support its conclusion only with some degree of probability; one of the two classes of argument. |

If the premises when true fail to establish the conclusion irrefutably although claiming to do so | the argument is invalid. |

Validity | A deductive argument is valid when, if its premises are true, its conclusion must be true. |

Valid Argument | If all the premises are true, the conclusion must be true; applies only to deductive arguments. |

Invalid Argument | The conclusion is not necessarily true, even if all the premises are true; applies only to deductive arguments. |

The central task of deductive logic | is to discriminate valid from invalid ones. |

Classical Logic | Traditional techniques, based on Aristotle's works, for the analyses of deductive arguments. |

Modern Symbolic Logic | Methods used by most modern logicians to analyze deductive arguments. |

Probability | The likelihood that some conclusion (of an inductive argument) is true. |

In Inductive argument | no claim of conclusiveness is made.The terms 'validity' and 'invalidity' do not apply to inductive arguments. |

Deductive Arguments Cannot Become Better or Worse | They either succeed or they do not succeed in exhibiting a compelling relation between premises and conclusion. If a deductive argument is valid no additional premises could possibly add to the strength of that argument. If an argument is valid, nothing |

Good Inductive Argument-It's First Premise is true, and IF it's second premise is true, it's conclusion is... | more likely to be true than false. |

New Premises Added to Inductive Arguments might weaken or (depending on the content of new premises) strengthen the original argument. | T |

Distinction between induction and deduction | rests on the nature of the claims made by the two types of arguments about the relations between their premises and their conclusions. |

Deductive Argument is | one whose conclusion is claimed to follow from its premises with absolute necessity, this necessity not being a matter of degree and not depending in any way on whatever else may be the case. |

Inductive Argument is | one whose conclusion is claimed to follow from its premises only with probability, this probability being a matter of degree and dependent upon what else may be the case. |

Truth is | An attribute of a proposition that asserts what really is the case. |

Truth and Falsity are attributes of individual propositions where as validity and invalidity are attributes of | arguments |

The concept of truth cannot apply to arguments, just as validity cannot apply to a single proposition. | T |

An argument may be valid even when its conclusion and one or more of its premises are false. | T |

The truth or falsity of an argument's conclusion does not by itself determine the validity or invalidity of the argument. The fact that an argument is valid does not guarantee the truth of the conclusion. | T |

If an argument is valid and its premises are true, we may be certain that its conclusion is also true. | T |

If an argument is valid, and its conclusion is false, not all the premises can be true.--Must have at least on false premise. | T |

Sound | An argument that is valid and has only true premises. |