Sentence:  It follows , then , provided the <WSD>possibilities</WSD> have been exhausted , that the only real alternative is the general viewpoint of the `` left '' , which has been represented on the Continent by Fritz Buri and , to some extent at least , is found in much that is significant in American and English theology . 
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