What does a sufficient assumption question on the LSAT look like?

Answer 1

Simply put, a sufficient assumption question asks you to pick an answer choice that, when added back into a given argument, will make the premises flow successfully to the conclusion.

The above description presupposes your understanding of 1) arguments and premises/conclusions; 2) what it means for an argument to "flow to the conclusion". So, let me explain these two briefly.

1) An argument is made of two parts -- premises and a conclusion. A conclusion is the main point of the argument; premises are support given to reach the main point. Typically, a sufficient assumption question gives you a paragraph that contains an argument and some background information (in harder questions, premises and conclusion are embedded within background information. So, your first job is always to clearly extract the argument from the paragraph and shelf parts that are irrelevant.

2) The kind of argument in a sufficient assumption question is typically a "bad" argument -- it currently lacks something between its given premises and its conclusion (or, in more technical terms, the given argument, prior to adding the correct answer choice, is an invalid argument, such that, when premises are taken to be true, the conclusion does not yet follow from premises). Therefore, your job in a sufficient assumption question is to choose, from the given choices, a "bridge" that would successfully connect the current premises in the given argument to its conclusion. For example, here's a stupid argument:

Premise 1: Bob is rich.

Conclusion: Bob is healthy.

Right now, this already-stupid argument is also bad, because my premise does not at all lead me to the conclusion I want to establish -- rich and healthy are two different things, and no relation between the two is at all established! Therefore, I need to add something to this argument, if I want to reach my conclusion! A sufficient assumption, in this case, is something that would lead me from "Bob is rich" to "Bob is healthy". Thus, one sufficient assumption here could simply be this: Anyone who is rich is healthy.

If I add this to the argument, now, my stupid argument is no longer bad (though still stupid):

Premise 1: Bob is rich.

Premise 2: Anyone who is rich is healthy.

Conclusion: Bob is healthy.

That second premise is the sufficient assumption I added to my original argument, in order to reach my conclusion.

To reiterate, a sufficient assumption is something that, when added to a given argument, will guarantee that the argument's conclusion is reached.

Sufficient assumptions are often contrasted with necessary assumptions. The distinction between the two question types is important, and should be studied thoroughly.