Inherent Inference Recognition Drill #5

[smarsh13@terpmail.umd.edu]

Hey! Quick question. I'm using the LR Bible 2020 edition and I'm struggling with drill #5 on page 441.

Would the translation of AFR <——s——> RP be "airlines sometimes fly a route if the route is profitable" or "some airlines fly a route if the route is profitable"?

My confusion is where to place the "some" in these statements.

Thanks!

[Jon Denning]

Good question! The answer is that both of those interpretations would necessarily be true/correct if we take the original statement as true: if all airlines always fly when a route is profitable (that's one half of the double-arrow original), then it must be the case that (1) some airlines fly when a route is profitable, and (2) airlines sometimes fly when a route is profitable.

You can do the same with the "most" implications: (1) most airlines fly when a route is profitable and (2) airlines fly most of the time when a route is profitable.

The great thing about statements containing language as strong/absolute as "all" (or "always") is that they typically guarantee a number of softer-language claims, as we see in this example, so really it just becomes about semantics in recognizing the various ways you can state those softer claims and the multiple constructions that still hold true. Good catch in considering a few different potential interpretations here!

[lsat2022]

I'm a bit confused with this one as well. Do we interpret "if and only if" as "all with " which is why we get both "most" and "some" inherent inferences?

Thank you!

[Dave Killoran]

Hi LSAT,

Yes, "if and only if" always produces a double arrow. Thus, "most" and "some" are inherently underneath that in both directions.

Thanks!