> From when I started, we’ve moved through Ruby 1.6, 1.8, 1.9, 2.0, 2.1, 2.2, and now onto 2.3. Lots of major changes along the way, but Rails was there to have Ruby’s back, and help everyone get with the program faster.

主要是說 Ruby 版本之間的大變化，Rails 都會跟進修改，所以是 Rails 當 Ruby 的後盾。