Which of the following statements correctly apply to deductive arguments? A. Deductive arguments are either valid or invalid B. There must be a necessary relation between the premises and the conclusion C. Adding new premises improves the validity D. False premises may lead to a true conclusion Choose the correct answer from the options given below :
A, B and D only
Understanding Deductive Arguments
Deductive arguments are a fundamental type of logical argument. In a deductive argument, the premises are intended to provide conclusive support for the conclusion. If the premises are true and the argument is valid, the conclusion must be true.
Let's analyze each statement provided in the question regarding deductive arguments:
Statement A: Deductive Arguments are Either Valid or Invalid
This statement is correct. Deductive arguments are assessed based on their validity. Validity in a deductive argument refers to the logical structure; specifically, whether the conclusion necessarily follows from the premises. An argument is valid if it's impossible for the premises to be true and the conclusion false simultaneously. If the conclusion does not necessarily follow from the premises, the argument is invalid. There is no middle ground between valid and invalid for deductive arguments.
Statement B: There Must Be a Necessary Relation Between the Premises and the Conclusion
This statement is also correct and closely related to validity. For a deductive argument to be valid, there must be a necessary logical connection such that if the premises are true, the conclusion *must* also be true. The conclusion is already implicitly contained within the premises; deduction makes it explicit.
Statement C: Adding New Premises Improves the Validity
This statement is incorrect. The validity of a deductive argument depends solely on its logical form or structure, not on the addition of new information or premises. Adding premises to an already valid deductive argument doesn't make it "more" valid. Similarly, adding premises to an invalid deductive argument doesn't make it valid (unless the added premises fundamentally change the core structure to a valid one, which isn't the typical implication of "adding"). This concept is more relevant to inductive arguments, where additional evidence (premises) can strengthen the likelihood of the conclusion.
Statement D: False Premises May Lead to a True Conclusion
This statement is correct. A deductive argument can be valid even if its premises are false. And if a deductive argument is valid but has false premises, it is possible for the conclusion to turn out to be true purely by chance or due to unrelated facts. Here is an example:
Premise 1: All birds are mammals. (False)
Premise 2: A robin is a bird. (True)
Conclusion: Therefore, a robin is a mammal. (False)
In this case, the argument is valid in form (Modus Ponens), but the conclusion is false because the premises are not all true.
Consider another example:
Premise 1: All fish can fly. (False)
Premise 2: All flying things live in the water. (False)
Conclusion: Therefore, all fish live in the water. (True)
Here, the argument is valid in form, the premises are false, but the conclusion happens to be true.
So, it is possible for a valid deductive argument to have false premises and a true conclusion. It is also possible for an invalid argument to have false premises and a true conclusion.
Based on the analysis:
- Statement A is correct.
- Statement B is correct.
- Statement C is incorrect.
- Statement D is correct.
Therefore, the statements that correctly apply to deductive arguments are A, B, and D.
The correct option is the one that includes A, B, and D.
| Statement | Applies to Deductive Arguments? | Reasoning |
|---|---|---|
| A. Deductive arguments are either valid or invalid | Yes | Validity is the core measure of logical structure. |
| B. Necessary relation between premises and conclusion | Yes | Essential for validity; conclusion follows necessarily. |
| C. Adding new premises improves validity | No | Validity depends on logical form, not amount of premises. |
| D. False premises may lead to a true conclusion | Yes | Possible in valid arguments with false premises. |
Revision Table: Key Concepts in Deductive Logic
| Term | Definition |
|---|---|
| Deductive Argument | An argument where the conclusion is claimed to follow necessarily from the premises. |
| Validity | A property of a deductive argument's structure; if premises are true, conclusion must be true. |
| Soundness | A property of a deductive argument that is both valid AND has all true premises. Sound arguments guarantee a true conclusion. |
| Premise | A statement or proposition that provides support for the conclusion. |
| Conclusion | The statement that is affirmed on the basis of the premises. |
Additional Information: Deductive vs. Inductive Arguments
It is helpful to contrast deductive arguments with inductive arguments to better understand their properties.
- Deductive Arguments: Aim for certainty. If valid and premises are true, the conclusion is guaranteed to be true. Assessed as valid/invalid and sound/unsound. New premises do not change validity.
- Inductive Arguments: Aim for probability. Premises provide support to make the conclusion likely, but not certain. Assessed as strong/weak. New evidence (premises) can make an inductive argument stronger or weaker.
The rules discussed in the question, such as validity and the necessary relation between premises and conclusion, are specific characteristics of deductive reasoning.
Important Questions from Argument Forms - Teaching
The Fallacy committed in the argument
"All textbooks are books intended for careful study. Some reference books are books intended for careful study. Therefore, some reference books are textbooks." is
- The space program deserves increased expenditure in the years ahead. Not only does the national defence depend upon it, but the program will more than pay for itself in terms of technological snipoffs. Furthermore, at current funding levels, the program cannot fulfil its anticipated potential”. What is the conclusion of the above argument?
All mortals are men.
Socrates is mortal
Therefore Socrates is a man.
Which of the following statements are true of the above argument?
(A) Above arguments is sound.
(B) Above argument is valid.
(C) Above argument is fallacious.
(D) Above argument commits the fallacy of undistributed middle.
Choose the correct answer from the options given below:"Environmentalists accuse us of blocking the plan to convert Antartica into a World park. In fact nothing could be further from the truth. Antartica is a huge continent teeming with life. It is home to millions of penguins, seals, seabirds and sea lions. Also great schools of finfish and whales inhabit its coastal waters."
Which fallacy is committed in the above argument?
Given below are two statements:
Statement I : An argument form that allows for a substitution instance having true premises and a false conclusion is an invalid form.
Statement II : Any arguments having true premises and a false conclusion is an invalid argument.
In the light of the above statements, choose the correct answer from the options given below :
