"No One"

[samuelfbaron]

Could someone please help me with understanding the implications of 'no one' in LR.

For instance: "no one who lacks knowledge of a subject is competent to pass judgment on that subject,"

Is there a synonym that I could replace 'no one' with?

[noah]

Could someone please help me with understanding the implications of 'no one' in LR.

For instance: "no one who lacks knowledge of a subject is competent to pass judgment on that subject,"

Is there a synonym that I could replace 'no one' with?

Good question.

Let's do a bit of back and forth on this.

If I say "no one who runs daily is overweight", which of the following do you know?

(A) If runs daily then not overweight. (RD --> ~ O)
(B) If not overweight, then runs daily. (~ O --> RD)
(C) If not running daily, then overweight. (~RD --> O)

The answer is (highlight text:) A is correct--and notice that the second two are logically equivalent to each other

So, what do you think we do with that "no one" to get to that answer?

Tell me a "technique" and then see how you do with each of these (logical translation after each one, highlight to reveal--and obviously it doesn't matter if you get the contrapositive or what I write):

1. No one that believes in Santa Claus is over 7 years old. BSC --> 7 or under (i.e. NOT over 7)
2. No one in the Navy Seals is a pacifist. N.Seal --> not pacifist

3. No one who lives in Las Vegas can avoid gambling.Las Vegas (baby!) --> NOT avoid gambling (or does gamble)
4. Look at that group of teenagers! It's clear that no one in the group is really happy. Teen in group --> unhappy

5. Looking at that group of teenagers it's clear that no child psychologist really understands adolescence yet. child shrink --> NOT understand teens

Did you come up with a "trick"? It's actually not important that you do, as long as you can quickly translate these, but, of course, it's fine if you do develop a strategy. Just make sure you don't completely replace thinking with a trick.

[samuelfbaron]

"no one who runs daily is overweight",

(A) If runs daily then not overweight. (RD --> ~ O)
(B) If not overweight, then runs daily. (~ O --> RD)
(C) If not running daily, then overweight. (~RD --> O)

(A) Can be inferred.

How are (B) and (C) logically equivalent? They are not the contrapositives of (A).

EDIT: Oh sorry, I didn't realize you meant (B) and (C) are the logical equivalent of each other. Yes, I see that (C) is merely the contrapositive of (B)!

I think the bigger issue from my statement that I posted was the use of the 'lacks'. That combined with 'no one' sortof implies way too much negation in the statement, which really confused me.

[noah]

"no one who runs daily is overweight",

(A) If runs daily then not overweight. (RD --> ~ O)
(B) If not overweight, then runs daily. (~ O --> RD)
(C) If not running daily, then overweight. (~RD --> O)

(A) Can be inferred.

How are (B) and (C) logically equivalent? They are not the contrapositives of (A).

I think the bigger issue from my statement that I posted was the use of the 'lacks'. That combined with 'no one' sortof implies way too much negation in the statement, which really confused me.

(B) and (C) are logically equivalent to each other.

The "lacks" is tricky!

If I had to boil it down: No one who is X does Y becomes If X, then not Y.

And so, No one who is X lacks Y becomes If X, then not lacking Y or, perhaps put more simply If X, then Y.

That clear it up?

[samuelfbaron]

Perfect! Thank you.

Learning conditionals and translating statements has sort of become a hobby / obsession of mine.