1. DEDUCTIVE AND INDUCTIVE ARGUMENTS Fundamentals of Logic Unit – 1 Chapter – 4 Fundamentals of Logic Unit – 1 Chapter – 4

2. Types of Arguments: Every argument makes the claim on the ground provided from its premises for the truth of its conclusion. The claim is the mark (sign) of the argument. The claim for the conclusion may be supported by two different ways. They have different ways of providing support for conclusion.

3. Types of Arguments: Arguments Deductive Inductive

4. Deductive Arguments: Deductive reasoning makes claim that its conclusion is supported by its premises conclusively (certain/true). A 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 on whatever may be the case. In other words, a deductive argument is that which first makes the conclusion that is followed by its premises.

5. Example: Premise Socrates is mortal. Premise Socrates is a human being Conclsion All Human beings are mortal

6. Deductive Argument: Deductive argument includes claim which is made on ground of its premises. Its conclusion can either correct or incorrect. If its premises are correct then its claim (conclusion) is also correct. Then the argument is valid. But if the argument fails to establish its truth, then it is invalid.

7. Contd… For logicians, the term ‘validity’ is applicable only to deductive argument. In other words, a deductive argument is valid, when its premises are true, its conclusion must be true. Deductive arguments that fail to do so are invalid.

8. Inductive Arguments: Inductive reasoning makes claim that its conclusion is supported by its premises with probability. An Inductive argument is one whose conclusion is claimed to follow from its premises only with probability; this probability being the matter of degree and dependent on what else may be the case. In inductive argument, premises come first proceeded by its conclusion.

9. Contd… Inductive argument is undertaken in empirical investigations. Such as: In medicine, social sciences, astronomy. In inductive argument, cause and effect relation is important e.g.  Cause and effect of inductive investigation on STD (Sexually Transmitted Diseases) Unlike the deductive argument, the claim or conclusion in inductive argument is seen with probability not with certainty.

10. Contd… Inductive arguments make weaker claims than those made by deductive arguments. Because their conclusions are never certain. The terms validity and invalidity do not apply to inductive arguments. Inductive arguments may be “better”, or “worse”, “weaker” or “strong” and so on.

11. Additional Information in IA: An inductive argument can give no more than some degree of probability for its conclusion. Therefore, it is always possible that additional information will strengthen or weaken e.g.  Most actors are celebrities.  Mahesh Parajuli is an actor.  Therefore Mahesh Parajuli is probably a celebrity.

12. Contd… But let’s see what difference is realized due to additional information.  Mahesh Parajuli is a theatre actor.  Most theatre actors are not celebrities.  Therefore Mahesh Parajuli is not probably a celebrity.Or  ( No theatre actors are celebrities.) So additional information has weakened the previous conclusion here.

13. Contd… New discoveries may disconfirm what was earlier believed. Therefore, conclusion of an IA can not be absolutely certained.

14. Difference bet Inductive and Deductive Arguments: Deductive Arguments Inductive Arguments 1.Conclusion is claimed to follow from its premises with absolute necessity. 2.It makes the conclusion that is followed by its premises. 1.conclusion is claimed to be supported by its premises with probability. 2.In inductive argument, premises come first proceeded by its conclusion.

15. Difference bet Inductive and Deductive Arguments: Deductive ArgumentsInductive Arguments 3. Its conclusion can either correct or incorrect. 4.Deductive arguments are either valid or Invalid. 4.There is not the matter of additional information. 3. Its conclusion comes only with probability. 4. The matter of validity and invalidity does not apply in inductive arguments but there is only the degree of probability. 5. Additional information may strengthen or weaken the IA.