I answered a question today in ProCopyClub from a member who is having trouble with editing. Every time they reread their copy, they come to the conclusion it needs more editing.
The problem is they see this (the need to edit) as a negative reflection of their skills (but it’s the opposite, it shows progress, they’re recognising the mistakes they used to ignore).
Ogilvy’s element 11 is kind of similar. The problem with most writing, not just copy, is a lack of focus on what matters (which is just one thing: the audience and the problem we’re fixing for them).
So if our first sentence or two (the hook or lede) promises something or another, then the rest of the copy better stick with that promise (which we call the ONE THING).
If it starts straying into other territory, then it immediately fails to live up to its promise (and we know what happens to politicians who fail to live up to their promises…).
See that last bit in brackets? That’s an example of straying.
We can be side-lined by clients too. Most of them have an opinion on how we should write copy, so we need to set their expectations right from the start (“my way or the highway baby”).
The point is, whatever we’ve decided to write about, we’d better stick to it like a magnet – if we’ve decided it’s the hottest thing since sliced bread, then we must make it so.
To do anything else is to dilute it (and diluting anything reduces its value). So I guess you could sum this element up as “go all in”, or in Ogilvy’s words: “go the whole hog”.