Sentence:  This circumstance in the patient 's case plus the fact that his tactual <WSD>capacity</WSD> remained basically in sound working order constitutes its exceptional value for the problem at hand since the evidence presented by the authors is overwhelming that , when the patient closed his eyes , he had absolutely no spatial ( that is , third-dimensional ) awareness whatsoever . 
Meaning of the word marked with <WSD> tags:  capability to perform or produce