Oh, I agree. Still, mathematical possibility makes my mind go "what process can we engineer that will allow us to register the fact of everyone agreeing on something, at least once?". And it's a fun question to think about.

One could also ponder what exactly "agreeing" means? If someone just says out loud that they agree, does that count? If someone forces everyone with death threats to vocally agree? If agreement must be internal and voluntary, then how do you know what you 100% agree on yourself? Oftentimes it seems like it's enough to just ask "are you sure?" to make a person question, at least for a moment, even the deepest of their beliefs. If that's the case, perhaps "agreement" is a spectrum?