Sentence:  This way of <WSD>escape</WSD> is theoretically possible , but since it has grave difficulties of its own and has not , so far as I know , been urged by positivists , it is perhaps best not to spend time over it . 
Meaning of the word marked with <WSD> tags:  nonperformance of something distasteful (as by deceit or trickery) that you are supposed to do