when and if

[Steve Long]

In a message dated 1/27/03 9:55:19 PM, bill_mann at SIL.ORG writes:
<< The use of either "when" or "if" in English can represent  "in a condition

in which" , and both words are actually common for this function.  "...When
we do so,... we use precious, limited resources...">>

"When" and "if" are interchangeable when the time element is future and
hypothetical, since both words refer to forms of uncertainty about a future
event.  The nature of the uncertainty ("if" versus "when") may often be
immaterial --- except for example where the contrast is made explicit, i.e,
"It's not a matter of if I do it, but when I do it."

However when we move the event to the past, the uncertainty and conditional
aspect of "when" disappears.  And the difference in senses becomes overt.

Compare:
--If you do that, you will hurt yourself
--When you do that, you will hurt yourself
To:
--If you did that, you will hurt yourself
--When you did that, you will hurt yourself

"If you did that, you will hurt yourself"
The future event is conditional upon an uncertain past fact.  The uncertainty
makes "if" conditional and thereby implies a connection between the two
events.  The statement seems to be a prediction contingent on a past event.

"When you did that, you will hurt yourself"
The change to "when" appears to render the sentence incomprehensible.
Because "when" used in referring to the past creates no condition or
uncertainty, it states a fact.  And so losing conditionality, we've lost the
connection between the past and future event.  The sentence simply looks like
a failure to create agreement between the verbs.

When we talk about the future, the difference between "if" and "when" is
obscured by both events being hypothetical and conditional in some way.  When
we talk about the past, the difference between the usages becomes apparent.
"If we lived in Dallas" means something quite different from "When we lived
in Dallas".

S. Long