Sentence:  While other conditions might be even more effective in bringing about a change from immobility to mobility in Kohnstamm reactivity , it <WSD>is</WSD> our hypothesis that all such conditions would have as a common factor the capacity to induce an attitude in the subject which enabled him to divorce himself temporarily from feelings of responsibility for his behavior . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)