I thought it might be ironic to write about consistency when my blogging lately has been so inconsistent.
Intelligentediting.com makes the point well:
Writers and editors must constantly seek to achieve consistency. Each inconsistency we remove eliminates a barrier between readers and understanding, facilitates communication, and thereby increases the likelihood that our writing will convey the message we intended. Readers learn the conventions we have used early in a manuscript and use that knowledge to facilitate comprehension of subsequent material. Editing for consistency thus serves two goals: it both eases the task of reading by teaching readers how to understand our writing and eliminates obstacles that would make that task more difficult.
Essentially, this means choosing a style and sticking with it. I’ve written a lot about rules that it’s okay to break and situations there is a choice between different rules to follow, especially here and here. The key is that you need to choose a rule and stick with it throughout your writing, or at least throughout a given work.
This is why most publishers, newspapers and other industries that deal with writing have a “house style” – to ensure that their publications remain consistent. If you pick up any well-edited magazine, you should be able to read it cover-to-cover without encountering variations in style.
Further reading: American Journal Experts on consistency in academic writing. Most of what they say applies to pretty much any type of writing.