"Introduction to Deductive Reasoning" by Leonard Peikoff

Introduction to Logic by Leonard Peikoff -- part 4: Introduction to Deductive Reasoning
Course playlist: • Introduction to Logic ...
This lesson covers the nature of deductive argument, including: validity and truth; mixed and pure hypothetical arguments; and alternative arguments.
Recorded in 1974.
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[@user-gy1ky9qe7w]

12:54 rules of validity of deductive argument 1)if something then something 16:00 2)either something or something 3)a straightforward categorical assertion with no if then and no either or "Categorical statements " 22:08 standard form Any one of them is valid they are all valid Purpose of symbolize is verify validity of structure 28:30 number 1 affirming the antecedent is valid Valid meaning conclusion follows 29:35 number 2 denying the antecedent is invalid Fallacy of denying antecedent Does not say only if Statement P implies Q gives you only sufficient condition of Q It says p is enough to produce Q If you have P you will get Q but it doesn't tell you that P is necessary to get Q It doesn't say you Have to have P to get Q This type of reasoning is invalid 36:00 number 3 Maybe something else other than P produce Q 37:45 number 4 44:50 mean that but they don't literally say it Only if P then Q reverse of if then statement If then statement gives sufficient condition Only if Statement gives necessary condition but it may not be sufficient 47:02 two different choices 1》drop only and negate both constituents Only p implies Q - P prime implies Q Prime 2》drop only and reverse constituents P implies Q 50:58 synonym of if (english)-conditional idea when, where,provided that,condition that, assuming that substitute if When men think then they prosper Ordinary language 》reverse of one thing depending on another He will pass if you motivated Standard form: if you motivated then he will pass 52:25 unless =if not Unless you study you fail If you do not study you fail

[@user-gy1ky9qe7w]

54:00 logical indicator (english) 》Conclusion Introduction by therefore,as, so,as a result ,I conclude, hence,consequently,thus 》Premise introduction by for,because,since,on the grounds that, on the premise that, my reason is 59:00 pure hypotheticals valid chain 1:04:25 rules of valid chain (sororities) Broken chain is invalid pure hypotheticals 1:10:54 1》premises may not have been presented in the right order 2》look for only's(two choices) Get ride of only 3》 general principle 》rewrite a statement P implies Q us identical to Q prime implies P Prime (reverse and negate) Number 5 1:22:02 alternative arguments 1:27:20 separate rules if validity for weak alternation Number 6 is invalid One alternate,another alternate 》Premise tell you one or other maybe both but atleast one must be true 》P2 maybe both true or maybe both not true Second premise tell you one alternate true we can't conclude anything about the other one 1:33:13 rule dictate weak alternation Fallacy of weak alternation 1:35:25strong alternation Either P or Q or not both one must be true at minimum one can be true at maximum Weak tells you if either is false the other is true but weak doesn't tell you if either is true the other must be false it leaves open maybe both 1:40:50 transform alternate to hypothetical P v Q rewritten as P prime implies Q Alternation to implication and negate the first 1:45:05 informal fallacy 15Q 2:01:30 informal fallacies 45Q

[@setemendigos6910]

1:43:00 Complementing: composition finds the possible generalizations between the elements of a set. Integration finds the relationships that exist between these elements and that are not contradictory.

[@adeelali8417]

1:44:55 Accumulated Questions + HW

[@adeelali8417]

Wow it has been three years!? Revisiting this now since I'm planning a critical thinking curriculum.

[@YashArya01]

2:01:30: Discuss previous homework