Inductive Arguments
Inductive arguments aim to provide premises that make the conclusion more probable than it otherwise would be. The inductive arguments aim to support the conclusion without making it unavoidable. The inductive arguments thus make their conclusions merely probable but not guaranteed.
Example
- Most men eat meat.
- John is a man.
- Therefore, John eats meat.
In this case, there is a high probability that John eats meat since most men eat meat. However, since all men don’t eat meat, it is not sure that John eats meat.
Inductive arguments are widely used in science. For example, if science makes a claim that ‘smoking causes cancer’, it does not mean that everyone who smokes is sure to get cancer. It only establishes that smokers have a high probability of cancer as compared to nonsmokers. Inductive arguments can be either strong or weak.
Strong and Weak Inductive Argument
Strong Arguments
A strong inductive argument is an argument that succeeds in having its conclusion be probably true, given the truth of the premises.
Example
- Most Germans have a fair complexion.
- John is a German.
- Therefore, John has a fair complexion.
The above argument is considered strong because John’s probability of a fair complexion is high.
Weak Argument
A weak argument is an inductive argument that fails to have its conclusion be probably true, even given the truth of the premises.
Example
- Most Germans have a fair complexion.
- John has a fair complexion.
- Therefore, John is a German
It is a fact that people of many nationalities (like England, America, Canada, Japan, etc.) have a fair complexion, and Germany is one such nation with a significantly smaller population as compared to the population of fair-complexioned people around the world. Since the probability of John being German is quite low, the above argument is considered weak.
Valid and Invalid Inductive Argument
The inductive argument involves the claim that the truth of its premises makes the conclusion more probable. Hence, the terms valid and invalid are generally not applied for inductive arguments. However, it is essential to understand that a conclusion is built on the strength of the premises, as the inductive strength of the conclusion comes from the probabilistic support that the premises confer upon the conclusion. Hence, the degree of truth of the conclusion can’t be more than the degree of truth of the premises. Thus, if the claim of the conclusion is higher than that of the premises, it is considered an invalid inductive argument because the conclusion does not follow from the premises.
Example
- P: 90% of humans believe in God
- P: John is a human
- C: John believes in God
In this case, the probability of John believing God can’t be more than 90%, while the conclusion is confirmative, i.e. 100% probability. Hence, it is not a valid argument. We can make the above argument strong and valid as follows.
- P: 90% of humans believe in God
- P: John is a human
- C: John most likely believes in God
However, the inductive arguments are not rejected because they are not strong. For instance, the following argument is strong but invalid.
- 10% of the smokers develop cancer.
- 1% of nonsmokers develop cancer.
- Hence, smoking causes cancer.
The conclusion is not perfectly valid because smoking does not cause cancer all the time, and all cancers are not due to smoking. However, this is considered to be a strong argument because if the premises are true, the probability of the conclusion being true is high because smoking increases the probability by 10 times. However, unless you have analysed the premises, you won’t know how strongly smoking is related to cancer. A layman may tend to believe on the basis of the conclusion that every smoker would get cancer. We can make the argument strong and valid as follows.
- 10% of the smokers develop cancer
- 1% of nonsmokers develop cancer
- Hence, smoking increases the risk of cancer by many (10) times.
The above argument is strong and valid because it is more transparent and does not make an assertion which is more probable than the premises.
