Quarter Wit, Quarter Wisdom: Making Sense of Assumptions

Today we would like to discuss a technique which is very useful in solving assumption questions. No, I am not talking about the ‘Assumption Negation Technique’ (ANT), which, by the way, is extremely useful, no doubt. The point is that ANT is explained beautifully and in detail in your book so there is no point of re-doing it here. You already know how to use it.

What we are going to discuss today is not so much a technique as a revelation of how you can identify the assumption in a particular argument by just fully understanding this – ‘what is an assumption?’. Actually, this is also already discussed in your CR book but I would like to draw your attention to it. We usually end up ignoring the finer points here and hence get stuck on something that is supposed to be quite obvious.

Ok so, what is an assumption?

An assumption is a missing necessary premise. (Doesn’t seem like much a revelation, right? You already knew that! Right! Focus on every word now.)

An assumption is a premise – it gives you some new fact/information.

It is also necessary – necessary for the conclusion to be true. The conclusion cannot be true if the assumption doesn’t hold. Our ANT is based on this premise.

To add, it is also missing – it is not something already mentioned in the argument.

Let’s take a very simplistic example to understand the implication of a missing necessary premise.

Argument: A implies B. B implies C. Hence, A implies D.

Premises given in the argument:
– A implies B
– B implies C

Conclusion given in the argument:
– A implies D

Is it apparent that something is missing here? Sure! The premises give us the relations between A, B and C. They do not mention D. But while drawing the conclusion, we are concluding about the relation between A and D. We can’t do that. We must know something about D too to be able to conclude a relation between A and D. Hence, there is a necessary premise that is missing here. What we are looking for is something that says ‘C implies D’.

When we add this to our premises, our argument makes sense.

Argument: A implies B. B implies C. C implies D. Hence, A implies D.

This little point will help us in solving the trickiest of questions. We get so lost in the n number of things mentioned in the argument that we forget to consider this aspect.

We will discuss an LSAT question today because it seems to be created just to exemplify this concept! Many people falter on this question. After going through it with us here, you will wonder why.

Question:

Therapist: The ability to trust other people is essential to happiness, for without trust there can be no meaningful emotional connection to another human being, and without meaningful emotional connections to others we feel isolated.
Which one of the following, if assumed, allows the conclusion of the therapist’s argument to be properly inferred?
(A) No one who is feeling isolated can feel happy.
(B) Anyone who has a meaningful emotional connection to another human being can be happy.
(C) To avoid feeling isolated, it is essential to trust other people.
(D) At least some people who do not feel isolated are happy.
(E) Anyone who is able to trust other people has a meaningful emotional connection to at least one other human being.

Solution:

First, we break down the argument into premises and conclusion.

Premises:

– Without trust there can be no meaningful emotional connection.

– Without meaningful emotional connections, we feel isolated.

Conclusion:

Ability to trust is essential to happiness.

Do you see something missing here? We are concluding about trust and happiness but in the premises, the link between ‘feeling isolated’ and ‘happiness’ is missing. The premises do not talk about happiness at all. So we need a premise which says, ‘feeling isolated’ means ‘not happy’ for the conclusion to make sense.
Look at the premises now:

Premises:

– Without trust there can be no meaningful emotional connection.

– Without meaningful emotional connections, we feel isolated.

– When we feel isolated, we cannot be happy. (The assumption)

Conclusion:

Ability to trust is essential to happiness.

Now it all makes sense, doesn’t it?

Look at the options now.

Option (A) says – ‘No one who is feeling isolated can feel happy.’ – exactly what we needed.

Hope this makes sense to you. Next week, we will see how you can easily solve OG questions using this concept.

Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!