Remember when we mentioned that symbols are awesome for referencing method names? Well, .respond_to? takes a symbol and returns true if an object can receive that method and false otherwise. For example,
[1, 2, 3].respond_to?(:push)
would return true, since you can call .push on an array object. However,
[1, 2, 3].respond_to?(:to_sym)
would return false, since you can't turn an array into a symbol.