It's maybe my favourite sentence in the world. Not because it's the first line of a great story nor because it encapsulates any human truth. It's because it works.
Here's the sentence: The cat sat on the mat.
OK, so what's so very special about that, then? Surely that's the kinda stereotypical pre-school learning-to-read sort of sentence that's about as basic as you can get? Well, yes. And that's part of its attraction and the point of this post.
Now, I was brought up and was primary-schooled in the 1970s, a time when there wasn't much attention being paid to the formalities of the English language. I can't recall being taught anything about how English works at all. That may be a credit to my teachers being able to sugar the pill of learning; it might not. So I'm coming to this late, and am slowly forcing myself to learn about language and linguistics, retrofitting the theory from the practice.
Let's take the sentence in question. It follows a standard English sentence format: subject, then verb, then object. Cat, sat, mat. SVO for short - subject, verb, object. It tells us a range of things: what's the subject of the sentence (the cat), then what it's doing (it's having a sit-down) and where (on the mat).
Also, the sentence dispenses with complex and/or unnecessary words. Neither adverb or adjective is present. We don't need them, so we don't have them. If there was a second moggy in the vicinity, then perhaps we'd need some description so we could tell them apart. There isn't so we don't. Same with the mat. Its colour, materials, texture; all of these are unimportant here.
I've used this in the past as a teaching sentence. It tells you everything you need to know about what's going on, and it isn't encumbered with unnecessary information. There's clarity, direction and purpose. Plus it's straightforward; we're not being sidetracked by the writer's overblown vocabulary or on their ability to flick through a thesaurus. We're just told what we need to know.
So it's a test I give myself; can I make what I've written any simpler? This is second / third / fourth draft working. First time round, just get the sense of what's going on down on the paper. Simplicity has to be worked at sometimes. And writing is always an iterative process.
Follow-up. There are seven basic sentence patterns in English. There's a useful list of them here. Note that they're all active (the subject comes first).