Quick question on has_many :thorugh

I was reading the documentation on this today and was wondering more
about the has_many :though, :dependent=>:destroy options. I am curious
how deep the deletes goes. Does it stop with the intermediate table or
does it pass through to the final table?

For example:
database
Categories (name, id)
Listings (category_id,product_id)
Products (id, name)

Assume in my Category Class I have
has_many :products , :through=>:listing, :dependent:=>:destroy

Now if I delete a Category, does it just delete the lisitng or does it
delete both the listing and the product?

Ben