No, blocks are not first class (procs are, and procs are the closest thing Ruby has to functions, and a method definition can bind convert the block passed to the function to a proc if a first-class value is needed.)

Blocks are a syntactically special single argument to a method that can either be yielded to (a Ruby construct similar to a function call but which only applies to the block passed to the current method) or converted to a proc (but the latter only as part of the method definition, since they aren't first class and thus cannot be manipulated or referred to directly.)