This is because readers will be able to weigh the arguments on either side against one another in a single place. It also means you yourself will have to consider a wider range of angles in reaching your conclusion, rather than making a one-sided search for arguments in favour of whatever you believe at the start.
A example of the problem with the alternative is Peter Hurford's post on 'EA Falling into a Meta-Trap' which is one of the most up-voted posts ever written here. I don't mean to pick on Peter in particular because most people naturally write 'the case for conclusion X', including me. Fortunately, as Peter is one of the most popular EA writers I don't feel like a jerk using him as an example.
Conveniently I disagree with Peter's conclusion and believe that EA has been, and is likely to continue, to under-invest in meta-charity. I don't intend to convince you that I'm right about that here - instead simply imagine the voice in my head as I'm reading that post:
- Here are some arguments against spending too much on meta-charity.
- Hmmmm, I've already heard most of these considerations before, but think they face very strong considerations on the other side.
- Oh, the blog post ended without considering the overall weight of the arguments on either side.
- And it didn't try to measure what fraction of our resources go to meta-charity, what fraction might go to meta-charity in the future, and what would be an appropriate fraction all things considered. It's completely consistent with everything in this post that the primary risk is actually spending too little.
Unfortunately, this means I didn't update my views that much in either direction, despite it being a very important issue to me. Which is a shame, because everything Peter wrote was sound in and of itself.
Here's an alternative structure for a post:
- Currently many people believe something like X (including me).
- Here are the best arguments that people offer in favour of that belief.
- Here are the best arguments / counter-arguments I can think of pointing in the other direction.
- Overall I think points A, B and C should be given most weight, which means my overall judgement is now Y.
- It's more boring to read because you usually won't offer a strident view that people disagree with, and it takes longer to read.
- It's at least twice as much work.
- Commenters will offer the counter-considerations anyway.