They are indeed all Proc objects:

    Proc.new {}.class
    => Proc
    lambda {}.class
    => Proc
    proc {}.class
    => Proc
    def block_class(&block) block.class end
    block_class {}
    => Proc

That write-up does have some great info in it, though.

Edit: there's an interesting comment on wycats' post that suggests the &block creates a Proc, and that blocks themselves are neither objects nor callable, ie, they can only be used directly with yield. That makes sense.

Even in that case, the original point still stands; we're still only dealing with Methods and Procs.