Sentence:  The authors set about answering this <WSD>fundamental</WSD> question through a detailed investigation of the patient 's ability , tactually , ( 1 ) to perceive figure and ( 2 ) to locate objects in space , with his eyes closed ( or turned away from the object concerned ) . 
Meaning of the word marked with <WSD> tags:  far-reaching and thoroughgoing in effect especially on the nature of something