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What is the difference between a presumption and an assumption?

Alum Member
in General 284 karma

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• Alum Member Sage
2459 karma

In regards to the LSAT, they are both premises. Assumptions are defined as unstated premises, whereas presumptions are stated premises (which we take to be true).

Hope this helps!

• Alum Member
277 karma

There are multiple definitions for each depending on which field of study you find yourself in. Philosophically speaking an assumption would be something made in the reasoning argument itself. A presumption is something you make before the argument I.e., a fundamental principle that exists in the authors worldview before he/she formulates the argument.

• Alum Member Sage
edited December 2019 796 karma

I think the difference is actually a bit subtle, and has to do more with differing levels of certainty than anything else.

Let's say I drop an apple. I "presume" that it will fall. Why? Because, well, gravity. And that's a pretty reasonable presumption. Now, let's say I give you an apple, I leave the room while you do some practice tests, and I come back and you haven't touched the apple. I'm shocked because I "assumed" you would have eaten it by then.

In the first case, gravity is a very reasonable thing to presume; while assuming you would have eaten the apple I gave you, though totally plausible, was a bit more shaky.

Now here's the caveat: generally, anytime you use "presume", you can also use assume. So I both presume and assume that an apple will fall. But it would be a bit weird to say that I presumed you would have eaten the apple, unless I really had reason to think so (like, if you told me that you really like apples and that you're hungry, or if there is statistical evidence that people usually eat apples within an hour when given one while doing practice tests).

So presume means the same thing as assume, but just narrows it down a bit more to things that you have reason to believe are true. But really, in effect, they're pretty interchangeable. And for purposes of the LSAT, any distinction between the two words shouldn't matter.