But which chain? From what I read, it's very important to distinguish between the true chain which full nodes can come to consensus on based on proof of work, a

But which chain? From what I read, it's very important to distinguish between the true chain which full nodes can come to consensus on based on proof of work, and a possible attacker chain which is longer, but low effort. https://cryptoservices.github.io/blockchain/consensus/2019/05/21/bitcoin-length-weight-confusion.html https://cryptoservices.github.io/blockchain/consensus/2019/0... And I believe I've read that, when you aren't running a full node, you have to just assume the longest chain is the right one. I mean, all that data is the chain, right? If you don't process it, you have to assume other nodes are trustworthy. What you are saying about complete control sounds to me like if I said I have complete control over my bank account, in the sense nobody can guess my password, but maybe the bank is fake and I'm not even trying to check.