We've all been burned by `NoMethodError: undefined method "___" for nil:NilClass`. One common path that leads us there is indexing arrays and hashes and attempting to chain method calls. Trying to capitalize the first string in an array? What if the list is empty? Trying to get a user profile bio? What if `profile` in `user.profile.bio` is not assigned? Let's take a step back from feature development and meditate on some Ruby fundamentals. In this talk, I'll cover some history and dangers of `nil` as a concept and how you can mitigate these vulnerabilities with Ruby's builtin `fetch` and `dig` methods for arrays and hashes.