Path helpers generate paths with dots instead of slashes

Yes, this is a pluralization error.

By passing the ID 1, I assume that you wish to display a single record.

So you need to use the singular 'message_thread':

message_thread_path(1)

Which will yield:

http://localhost:3000/message_threads/1

Sometimes this also is when you don't provide an :as parameter in your route:

delete "delete/:id" => "home#delete"

Changed to:

delete "delete/:id" => "home#delete", as: :delete

(ignore the odd example, just happened to be something we just ran into for an internal app we're building)