“First, it sounds unintelligent. Second, it sounds weak. And third, I just don’t get it. Why add the ‘ly’?”
I respectfully disagree that it sounds “unintelligent.” It sounds a bit stuffy or overly formal, perhaps, but not unintelligent. In fact, in British English, firstly tends to be preferred.
But in American English, we tend to prefer first.
Although, oddly enough, I’ve actually seen people begin with first and then follow it with secondly. That sounds closer to something that’s “unintelligent” to me. At least you should follow the same pattern throughout: either end with -ly or don’t…but don’t mix it up.
As Baumann points out in his response, the biggest argument against those -ly forms is the awkwardness that can potentially happen if you have a lot of items on your list: how many times have you ever heard someone use words like seventhly, eighthly, ninthly, etc.?
Patrick is a Christian with more than 26 years experience in professional writing, producing and marketing. His professional background also includes social media, reporting for broadcast television and the web, directing, videography and photography. He enjoys getting to know people over coffee and spending time with his dog.