There's a nursery rhyme that starts like this:
This is the house that Jack built.
This is the cheese that lay in the house that Jack built.
This is the rat that ate the cheese
That lay in the house that Jack built.
This is the cat that chased the rat
That ate the cheese that lay in the house that Jack built.
This is the dog that worried the cat
That chased the rat that ate the cheese
That lay in the house that Jack built.
This is the cow with the crumpled horn
That tossed the dog that worried the cat
That chased the rat that ate the cheese
That lay in the house that Jack built.
and continues in a similar vein. We might imagine the following conversation.
A Oh, that was a nice cheese I sold to Jack the other day!
B Which cheese?
A The cheese the rat ate!
B Oh, OK. Hang on, which rat?
A The rat the cat chased, of course!
B Ah, so you're talking about the cheese the rat the cat chased ate, then?
A Um, what...?
B Well, you said it was the cheese the rat ate, right?
A Yes...
B The rat the cat chased?
A That's what I said.
B So it's the cheese pause the rat the cat chased pause ate!
A Haha, OK, I suppose so, but it doesn't sound right!
B Which cat is this, then?
A sigh...
The conversation continues in a similar way, until eventually...
B So you're talking about
the cheese
the rat
the cat
the dog
the cow tossed
worried
chased
ate
then?
A ???!!?
If we're going to use the full nursery rhyme, then the cheese in question is actually
The cheese the rat the cat the dog the cow the maiden the man the judge the cock the farmer owned woke married kissed milked tossed worried chased ate!
If that doesn't make sense to you, then don't worry - it shouldn't, if you're human! But it really is an interesting fact that this sentence doesn't appear to make sense. In contrast to what Mr Blow keeps saying, it really is not 'just that simple'. The strange thing is that while the individual parts
the cheese the rat ate
the rat the cat chased
the cat the dog worried
the dog the cow tossed
all make sense, we can't paste them together using logical rules and arrive at an understandable sentence. This is surprising: normally, we could replace the phrase the cheese
in the sentence
The cheese was delicious.
with the cheese the rat ate
to arrive at
The cheese the rat ate was delicious.
and we can make as many such substitutions as we like, so
The maiden bought the cheese from the judge.
becomes
The maiden the man kissed bought the cheese the rat ate from the judge the cock woke.
which, though clumsy, still makes perfect sense. It's only when we start to introduce defining clauses within defining clauses that our usual substitution rules stop giving us sentences which we can process.
It is a peculiar limitation of the human brain, not a formal rule of language, that means that the phrase
the cheese the rat ate
makes perfect sense, the phrase
the cheese the rat the cat chased ate
can be understood, but only with difficulty, and the longer phrases above look like complete gobbledegook.