NTA-NET (UGC-NET) Philosophy (03) Video Course Lecture: Truth and Validity – Meaning of the Two Most Important Principles of Logic; Truth and Validity. 7 Examples to Judge the Validity and Invalidity of Arguments or Syllogisms with True and False Premises and Conclusions. Concept of Validity and Soundness (36 mins) | Lecture 310 of 355

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  • Logic-Formal and Symbolic » Truth and Validity,Denotation and Connotation

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Western Logic; Truth and Validity – Meaning of the two most important principles of Logic; truth and validity. 7 examples to judge the validity and invalidity of arguments or syllogisms with true and false premises and conclusions. Concept of Validity and Soundness

Understanding the 2 principles of Logic; understanding what is logic and what is Truth and Validity.

Understanding with seven examples;

  • Valid argument with true premises and conclusion
  • Valid argument with false premises and conclusion
  • Invalid argument with true premises and conclusion
  • Invalid argument with true premises and false conclusion
  • Valid argument with false premises and true conclusion
  • Invalid argument with false premises and conclusion, etc.
  • Understanding what is a Sound argument or syllogism with example

References: Introduction to Logic by Copi, Cohen and McMahon, Symbolic Logic by Copi.

Question: Validity condition = Conclusion derived from premises; Invalidity condition = When the middle term is not distributed; is this correct?

Answer: When Middle term is not distributed is one. . it can also be when middle term shows up in the conclusion. Please go through formal fallacies once, there we have discussed all the rules for valid and invalid arguments

Question: At the start of the video, you said that validity has nothing to do with the truth but all the examples are dependent on the truth of the argument. I՚m confused.

Answer: Validity and truth are two very different things. For example, Truth is the quality of a statement, it can be accurate, it can also be inaccurate. Validity is when the argument is valid then its conclusion necessarily follows logically from both the premises.

Question: In first example 10.53 time, both premises don՚t have distributive middle terms, but they are valid. Then why is 3rd example: with no distributive middle term - invalid, it should be valid right?

Answer: the first example, all doctors are health workers … here the subject term is being distributed. In an A proposition- the subject term is distributed and the predicate term is undistributed. The third example is invalid for the simple reason that there the middle term social service men is not distributed in either of the two premises.