Sentence:  To do this , it is sufficient to point out that if the principle in terms of which alternatives are to be conceived is such as to exclude more than two , then the question of a `` third '' <WSD>possibility</WSD> is a meaningless question . 
Meaning of the word marked with <WSD> tags:  a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena