7/28/2019 Assumptions.pdf

1/2

Assumptions Part 1:Arguments and Necessary Assumptions

What exactly is a Necessary Assumption?A necessary assumption is an assumption that the author MUST make in order to drawher/his conclusion from the available evidence. In other words, the argument CANNOT

work if this assumption is not true. Lets take a look at a test-like example:

Manny works night shifts at the local bodega, but he is extremely

interested in a part-time position at a call center that requires

him to work nights. Since Manny is already working at that time,

it stands to reason that even if he is selected for the call

center job, he will be unable to accept their offer.

First, lets identify the conclusion of the argument as well as the supporting evidence.Remember that the conclusion of an argument is its main idea it is the point of viewor idea of which the author is trying to convince you. Conclusions will be supported byother statements in the argument, as opposed to providing support for other statements(unless youre dealing with an argument containing multiple conclusions in which caseone conclusion could support another). Statements that provide support for conclusionsconstitute evidence.

In this case, we can split the argument up as follows:

Conclusion: Even if he is selected, Manny cannot take the call center job.

Evidence: The call center job requires Manny to work nights, and Manny is already

working nights at the local bodega.

Now, what must we assume in order for the conclusion to follow logically from theevidence? Take a few seconds to think about this and then read on.

When youre ready, evaluate each of the following statements and read the analysis thatfollows.

All call center jobs require working at night.

Nope. We know that this particular call center job would require Manny to work atnight, and thats as much as we need to know. We dont need to assume anything aboutall call center jobs.

It would be impossible for Manny to continue working at the

bodega while also working remotely for the call center from the

bodega.

7/28/2019 Assumptions.pdf

2/2

We have to assume that this is true. If it is possible for Manny to work both jobssimultaneously, then the conclusion clearly does not follow from the available evidence,since working at the bodega would not necessarily prevent Manny from accepting the callcenter job.

Call centers are willing to consider hiring someone who works ata bodega.

Tempting, but certainly not necessary. Heres where it helps to pay close attention to theconclusion of the argument and the issues contained within it. The conclusion is notabout whether or not Manny can be selected for the job. It is about whether he canaccept the job IF he is selected. Even if Manny cannot be selected, the logic of theargument is unaffected i.e. the conclusion can still follow from the evidence.

Manny cannot quit his current job at the bodega.

This was probably the first assumption that sprang to mind for many of you. If it was,then congratulations. You are correct. We have to assume that this is the case. If Mannycan in fact quit his current job, then he certainly could accept the job at the call center,thereby breaking the connection between the available evidence and the authorsconclusion.

Identifying necessary assumptions can be hugely helpful on other question types as well.For instance, an answer choice that validates a necessary assumption would make anexcellent candidate for the correct answer to a strengthen question. Conversely, an answerchoice that gives you reason to doubt a necessary assumption would make an excellent

weakener.

Next time: Well take a look at a more difficult example of a Necessary Assumptionquestion. Well also delve into a technique called the Negation Test, which will formalizethe process we just employed to identify assumptions that are truly necessary to theargument being made.