I beg to differ; obviously no hard proof to back this up but I expect that "I think" is used to express an opinion as much as it is to express uncertainty. Als

I beg to differ; obviously no hard proof to back this up but I expect that "I think" is used to express an opinion as much as it is to express uncertainty. Also uncertainty is presented in delivery and tone too; so distinguishing the two is relatively easy. When uncertain main emphasis is on the word "think". In an opinion (where you have conviction) the emphasis is on "I"