Assumption vs Inference

[DatsunB210]

The explanations I've seen so far...sufficient, necessary, etc. just aren't clicking with me.

Can anyone offer an everyday style, clear to understand breakdown of what an assumption is what an inference is and the difference between the two?

Much obliged.

[DavidG@VeritasPrep]

The explanations I've seen so far...sufficient, necessary, etc. just aren't clicking with me.

Can anyone offer an everyday style, clear to understand breakdown of what an assumption is what an inference is and the difference between the two?

Much obliged.

In an Inference question, you're missing a conclusion. In an Assumption question, you're missing a premise.

Take the prototypical syllogism:

All men are mortal ---> Premise 1
Socrates is a man ---> Premise 2
Therefore Socrates is mortal ---> Conclusion


In an inference question, you'd be given:
All men are mortal
Socrates is a man

Your job would be to infer the conclusion that Socrates is mortal.

In an assumption question you might be given:
All men are mortal.
Therefore Socrates is mortal.

Your job would be to see that we're missing the premise (assumption) that Socrates is a man.

This is obviously a radically simplified version of what you'd see on the test. The point is that the distinction comes down to which component of the argument we're missing.

[ceilidh.erickson]

David gives a great explanation of what these terms mean. I understand your confusion about how we talk about them, though.

When you get a Find the Assumption question ("which of the following is an assumption on which the argument depends?"), we're looking for that missing Premise 2, as David showed. In other words, you're looking for the thing that we don't yet know is true (because the author didn't state it), but that would HAVE to be true for the Conclusion to follow from Premise 1. Without it, the conclusion falls apart. In other words, it is NECESSARILY to make the argument logically cohere.

When you get a Draw an Inference question ("which of the follow must be true," "what conclusion can be drawn," etc), you're also looking for something that HAS to be true - something that flows logically from the premises given. The difference is generally that nothing else "falls apart" if the conclusion is untrue. Everything else stated is fact, so it can't really fall apart. In fact, we're looking for the thing that we can't make untrue.

To simplify:
Find Assumption: ask yourself, "does this statement have to be true for the conclusion to hold up?"
Draw an Inference: ask yourself "does this statement have to be true?" (full stop).

Does that clear things up?