However, the rule for finding the predecessor is no longer admissible, because there is no way to derive − 3 n a t {\displaystyle \mathbf {-3} \,\,{\mathsf {nat}}} .
但是，找到前驱者的规则不再是可接纳的，因为没有方式来得到 − 3 n a t {\displaystyle \mathbf {-3} \,\,{\mathsf {nat}}} 。