In this article, the following topics are discussed:

  • Some Standard Categories of Assumptions
  • When is an assumption invalid?
  • When an assumption can be outrightly rejected?
  • When an assumption cannot be outrightly rejected?


Existence/Non-existence of the subject:

This category makes a simple assumption of what is being talked must exist and absence of the subject must be non-existent.


Statement: Love marriages mostly end in divorce.

Valid assumptions: a. Love marriages take place.

  1. In few cases divorce takes place.

Existence Explanation

Statement: Love marriages mostly end in divorce.

What exists in this topic/statement?

Love marriage and divorce exist in the topic/statement, hence both assumptions are valid.


Statement: The company will not go into profit unless a foreign-trained manager is brought.

Valid Assumption: At present there are no foreign-trained managers in the company.

Non-existence Explanation

Statement: The company will not go into profit unless a foreign-trained manager is brought. 

Why the company will not go into profit?

Because there are no foreign-trained managers in the company. Conclusion is dependent on the given premises, hence valid assumption.


The quality of the subject makes the assumption to be valid.


Statement: The social nature of man leads to cooperation and coordination within the society.

Valid assumption: Man is social.

Adjectives Explanation

Which quality leads to cooperation and coordination within the society?

The social nature of man. The premise brings the conclusion, hence ‘man is social’ is valid assumption.


Statement: The bright-red sky looked beautiful enough to bring out the poet in him.

Valid assumption: The sky appears sometime bright-red.

Adjectives Explanation

What quality brought the poet in him?

The bright-red sky which was beautiful brought the poet in him. The premises bring the conclusion, hence valid assumption.

Cause & Effect:

It can be categorized as cause with effect, cause without effect and although cause yet no effect, no cause no effect.

Example for cause with effect

Statement: The ground is slippery, it must have rained.

Valid assumption: Whenever it rains, the rain converts the ground into slippery.

Explanation: The cause is rain and its effect is slippery ground.

Example for no cause and for no effect

Statement:  As you do not have the expertise, you cannot be selected.

Valid Assumption:  Expertise is essential for selection.

Example for, although cause yet no effect

Statement:  Although the city was under knee-deep water for four days in this monsoon, yet there was no outbreak of cholera.

Valid Assumption: Water-logging usually leads to cholera.

Course of action:

Sometimes a fact/report/observation/study/data is given followed by a suggested course of action. Let us call the given fact/data etc X and the suggested course of action Y. Then either some negative aspect of X is mentioned and a course of action Y is suggested or some positive aspect of X is mentioned and a course of action Y is suggested. In the former case, i.e., when some negative aspect of X is mentioned, the following assumptions will be valid. 


Statement: The Delhi High Court in a recent verdict has directed the Election Commission (EC) to compulsorily provide information to the voter through media about criminal background of candidates standing for assembly or parliamentary elections


1 Candidates with criminal background are harmful to the society.

2 Proper information will restrict candidates with criminal background standing for assembly or parliamentary elections.


In some cases it is concluded that, because a cause leads to some effect in one type of objects, it will also lead to the same effect in another type of objects. This is an example of reasoning by analogy. In such cases it is assumed that “The effect of the cause on both the species is similar.


Statement:     Properly-fed and starved monkeys were made to run through a maze (puzzle). It was seen that starved monkeys could not make their way fast. This proves that the lower intelligence of people in poor countries is the result of malnutrition.

Valid Assumption: The effect of malnutrition on the intelligence of the monkeys is parallel to those on human being.


In the examinations of today, the statements are usually in the form of an advertisement or an official notice or a notice issued in public interest or an appeal.

  1. An advertisement, an appeal or a notice does have any effect.
  2. In case of an advertisement, that which is being highlighted is looked for and expected by the people.
  3. In case of a public-interest notice, it is the duty of those who issue it, to issue such notices.
  4. In case of a public interest notice, what is being advised must be beneficial for people and its non-practice harmful in some ways.
  5. In case of an appeal, the reason for issuing it exists (you can determine the reason using your common sense).
  6. In case of an official notice, the effect of its implementation will be beneficial for the organization.

Example 1

Statement: Professional Tutorials-the only training institute that gives   exclusive articles on reasoning and mathematics

– an advertisement.

Valid  Assumption

  1. The advertisement will have some effect on those who read it.
  2. People look forward to exclusive articles on reasoning and mathematics.

Example 2

Statement: From next month onwards, it has been made compulsory for every worker to submit a daily report. – a notice issued in a company. 

Valid  Assumption

  1. The appeal will have some effect on people.
  2. The daily submission of reports by workers will prove beneficial for the company.

Example 3

Statement: Donate money for the earthquake victims. – an appeal.

Valid  Assumption

  1. The appeal will have some effect on people.
  2. There has been an earthquake and the condition of the earthquake victims is pitiable.

Example 4

Statement: Please do not lean out of the running train. – a notice in the railway compartment. 

Valid  Assumption

  1. The people are likely to pay attention to this notice.
  2. It is the duty of the Railways to issue such notices.
  3. Leaning out of running train is dangerous.
  4. Not leaning out of running train ensures safety.


To find out when an assumption is invalid is of equal importance. We have discussed the validity of assumption. Now, we should also see the cases and reasons where an assumption becomes invalid.


These assumptions are very easy to be shown incorrect because they are either just contrary to what the given statement says or they seem to have simply no connection with what the given statement says. Only a look at them will be enough to declare that they are not valid assumptions for the given statement. 


Statement: The government has increased the price of petroleum products.

Invalid Assumption: The price of petroleum products was very low

Reason: We are not sure whether the prices are very low or not.


These are circumstances where the given assumption is likely to force you to do some thinking. Some important categories of such assumptions are

Restatement: An assumption will be invalid if it is a mere restatement – putting it in different words of the given statement.

Obversion: Obversion is a slightly different case of restating the same fact. In it, two of the trio (subject, verb, predicate) are changed into negative which changes the appearance of the sentence without changing its meaning. An obverted form of the statement is an invalid assumption.

Inference: The given assumption is invalid if it is an inference derivable from the given statement. An assumption is something on which the statement is based and not something which itself is based upon (an inference of a statement is based upon the statement) the statement.


Statement: Political freedom is incomplete and has little meaning without economic independence.

Invalid assumption: Economic freedom is an essential virtue for any country.


The Critical reasoning question consists of a short passage followed by questions like –

“Which of the following best serves as an assumption that would make the argument above logically correct?” Read the question before you read the passage, so that you know that without the assumption plugged in, the conclusion will not hold.

If you decide to read the passage first, it may appear to be perfectly reasonable. It is only when you read the question that you realize that you have missed something or that there is a flaw in the reasoning. You will therefore have to go back to the passage. To avoid such a waste of time it is advisable to read the question first.