Here's a classic riddle (whose statement I am totally butchering, but that's ok!): "A man is carrying a canister of liquid which he claims to be a universal solvent. How do you know he's lying?" This text here is a bit of filler warning you that I'm going to spill the answer to this riddle in the next paragraph. So, if you want to figure out the riddle first, stop reading now before you accidentally get to the answer, because the answer is coming up soon. Ok, if you're reading at this point you don't mind having it spoiled. The answer is that if it was a universal solvent, then it would dissolve the canister which contains it! Now, for some odd reason I was thinking about this riddle, and realized I don't like the answer; couldn't a universal solvent become saturated, in which case it thus couldn't dissolve its container?