Sentence:  While the interpretations that have been given <WSD>are</WSD> inferences only , they gain support from such comments as the following , which was made by one of the Kohnstamm-negative subjects who did not , on the first trial , perceive the tilt illusion . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)