I'm having trouble truly understanding the meaning of "sufficiency". I just don't see if directly translating from its everyday definition to the logic definition/function. Could somebody help me understand it?

honestly I feel like at this point in the lessons, it just gets more confusing if you keep trying to understand every micro section of information. I think the best option is to just skim the information and come back after understanding the big picture later on

I don't understand 3.1. Like in my head, the sentence talking about the study linguists did is evidence for the first sentence(conclusion)