In simplest terms the possibility of metaphysics is equivalent to the existence of freedom (of the will). But if metaphysics is impossible it cannot be provably impossible, or more weakly, known to be impossible, since that would constitute metaphysics. So, if there is no freedom of the will there can be no valid acknowledgment of this unfreedom since it would have to be a free acknowledgment. That there are cases where metaphysics is taken to prove the absence of freedom of the will, is only because of the 'of the will' part of the assertion, which was always problematic, since this way of phrasing it brings with it a lot of baggage that is easily targeted. All of the key words here have to be interpreted generously, but that does not necessarily render them void. The same understanding can be banished at one level of interpretation only because it reappears at another. So that the acceptance of levels of interpretation is also equivalent to the possibility metaphysics.