At 2:04 PM -0400 6/29/06, eric.dunn at wrote:
>Firstly, logically speaking, isn't there a difference between:
>- If A, and then B
>- If A and B

 From the point of view of someone who is used to such structures in 
programming languages the first variant would never be used; the "and" would 
simply not be there.

 Once you remove the "and" the meaning is clear. If "condition specified by A 
is true" then "condition specified by B is also true. And example might be 
(with apologies to the exceptional duckbill platapus)  If it nurses its young, 
then it is a mammal. Note that if you stick the "and" in there it changes 
everything, and as someone noted earlier, it makes the sentence incomplete.

 As for the second variant, it means quite simply "If the condition specified 
by A is true and the condition specified by B is also true, ..." but it also 
needs to be completed with some kind of outcome, generally specified by a 
"...then..." construct.

>The first implies a wait or sequence between events A and B. It does not
>imply that the events are simultaneous nor that they need to be
>maintained. If A happens, stops, then six months later B happens, the
>first statement is true.

 No. If you interpret it that way you need to have some consequence to complete 
the idea.

> The second statement is true only while both
>events are happening (and they could start in any order).

 Not necessarily "events happening"; more often than not it's "existing 

>Secondly, Why does the sentence even contain "then" in the first place?
>(You don't even include THEN in If statements in many languages.)

 Because that's how the logic is described in words when B is a subset of A, or 
a condition that is always true if A is true.

 Folks seem to be tackling this from a grammatical perspective and consulting 
style manuals. These constructs come directly from the language of mathematics. 
The addition of the word "and" (which is a logical operator in its own right) 
just serves to confuse what is perfectly clear without it by making a complete 
thought incomplete (both logically and gramatically).

 - web

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