Sentence:  Hereby , the external object viewed by the eyes remains the thing that is <WSD>seen</WSD> , not the retinal image , the purpose of which would be to achieve perceptive cooperation by stirring sympathetic impulses in the other sensory centers , motor tensions , associated word symbols , and consciousness . 
Meaning of the word marked with <WSD> tags:  perceive by sight or have the power to perceive by sight