Sunday, June 15, 2008
My trailer, which is also on fire, is a Winnebago
The main idea of the sentence is that the trailer is a Winnebago. That the trailer is on fire has little to no bearing on the company that manufactured it; it's just an interesting little sidenote.
"That" should be used when you need to make a distinction, such as
Of all the trailers, mine is the one that caught fire
If you're not sure whether you're writing a distinction or an aside, try adding "by the way" after each "that" or "which"; if it seems right, then it's probably "which"; if not, it's probably "that."
Or you could just read this sentence by Nietszche
That which we find words for is that which we cannot hold in our heart
until you go insane.