"at least I mean what I say"

IZQuotes

Which two of these statements mean the same?

1. Every draft is a Bill of Exchange
2. Every draft is not a Bill of Exchange
3. No draft is a Bill of Exchange

Number 2 means the same as number 3. Number 1 means the opposite. Easy, right? You'd think so.

How bout this:

1. Some drafts are Bills of Exchange.
2. Some drafts are not Bills of Exchange.
3. Not every draft is a Bill of Exchange.

All three are equivalent this time.

When you say "not every one of them is X" it means NOT ALL of them are X, but SOME are.

When you say "every one of them is not X" it means NONE are X.

If I say "all of them are X" it should be obvious what I mean. If I say "all of them are NOT X" it should be equally obvious what I mean. When I say "ALL of them are not" I do not mean SOME of them are. I mean ALL of them are not, and NONE of them are.

Petty, right? But if you don't know petty stuff like this, you cannot say things that are logical. And if you try, you will probably get things wrong.

Here's a clip from pages 215 & 216 of The Foreign Trade of the United States: Its Character, Organization and Methods, a Google Book by Lillian Cummings Ford and Thomas Francis Ford. At the bottom of page 215 is part of the phrase "Digitized by Google":

I don't know what the hell that paragraph means.

They point out that in common usage, the terms "draft" and "bill of exchange" mean the same. Then they say that "strictly", NO draft is a Bill of Exchange. I think they mean to say that, strictly, only SOME drafts are Bills of Exchange. But they don't say SOME. They say ALL. They say ALL ARE NOT.

I can read the following sentence, where they say "a draft is not necessarily a negotiable instrument". The "not necessarily" part tells me that some drafts are negotiable and some are not. So the word SOME comes in by a back door.

They repeat the confusion in their last sentence: They say Bills of Exchange are the most common form of draft (again implying SOME) but conclude by stating clearly that "every draft is not a bill of exchange." No draft is a bill of exchange. That's the conclusion of the paragraph, and that's what they want me to understand.

No draft is a bill of exchange.

Look... I think I can figure out what they mean. But if I am using their book to learn something, the only thing I learn for sure is that they do not say what they mean.

In fact, they say the opposite of what they mean!