Kant Substantial self

Kant states that it has long since been known that the substantial self; that which is left over after all accidents(as predicates) have been taken away, is unknown. Pure reason leads us to an infinite regress of predicates, and nothing we reach can be taken as a final subject, and the substantial can never be thought by our understanding. Hence all real properties through which we know bodies are nothing but accidents, which one must always represent to oneself only as the effect of a force of which we do not have the subject. What we can see as substantial is the consciousness of ourself; for all predicates of the inner sense refer to the I as the subject, and the latter cannot be thought further as the predicate of any other subject. The absolute self is given in experience. But since the I is only a designation of the object of the inner self as we know it through no further predicate, and since it cannot itself be a predicate it cannot be a determinate of the absolute subject, but only the reference of the inner appearance to the unknown subject of them. Kant says this idea destorys all materialist explanations of the soul. And cognition of the the thinking being falls outside the sum total of experience.