Well for me it depends how it comes. If I make it and have it in a bowl, I eat it. If I make a quick Cup-A-Soup and have it in a mug, I drink it. I suppose, subconsciously, for me, the answer depends on whether cutlery is used. If I use a spoon and a bowl, I'm eating it. If I'm sipping it out of a mug, I'm drinking it.
I certainly don't want to start another fracas with Indiesinger! But - since it is basically liquid, however thick - soup is drunk, not eaten, regardless of the sipping/spooned approach to it in my opinion.
Tricky one this. I can see Monsiuer Le Quiz's pov, but surely that arguement falls down when you've got a good home made soup and you've got to chew on all the veg or ham, or even noodles/pasta. Hmmm.. OK: if you've got to chew it, then it's "eat" but no chewing = "drink". Depending on if it's in a mug or a bowl. Or if you soak it into crusty bread. Or... AARRGGHH! I dunno.
People drink soup, because it is a liquid. If there are bits in it which need to be chewed, then one has to eat the bits, but not the soup itself. In answer to thewillow's question - yes it does matter. People who incorrectly try to pretend that soup is "eaten" are intrinsically evil, and should be drowned in a large bowl of soup.
I have to agree with Indiesinger, soup is eaten if it in a bowl, (hence cutlery) and drunk from a cup.
What about Apple pie and custard? you don't eat the pie and then drink the custard, do you?
Well, the matron in my school always insisted that "one eats one's soup". I suppose that's because you have to use cutlery (if it's in a bowl, of course).
But I would agree with the above about drinking a Cuppasoup!