From the same Wikipedia article: "The identifier of a regular "function" in Ruby (which is really a method) cannot be used as a value or passed. It must first

From the same Wikipedia article: "The identifier of a regular "function" in Ruby (which is really a method) cannot be used as a value or passed. It must first be retrieved into a Method or Proc object to be used as first-class data. The syntax for calling such a function object differs from calling regular methods. Nested method definitions do not actually nest the scope." You can certainly make the case that Ruby has first-class functions, but they don't feel very first-class in practice.