Sentence:  In him you simply have nature's top-notch imitator. He never questions, he never asks why. . . . His brain, the conscious, active, <WSD>superliminal</WSD>, is not able to grasp a situation and reason it out. 
Meaning of the word marked with <WSD> tags:  Of, pertaining to, or involving conscious awareness; above the threshold of the subconscious.