[swagonomixxx]

Either the proof is incorrect or he/she set it up in a way to make it look extremely trivial.

The way I saw the proof go is: to satisfy CAP, you need replication, and you need high availability. To be consistent you need replication. But if you don’t have a reliable network, you don’t get reliable replication. Therefore you can’t be consistent. To me, this is a trivial result, and I’m not sure that this is what the CAP theorem intends to say?

It would be better to do, as you say, assume that a system is CA, And prove why it can’t be partition tolerant. Saying “network is unreliable” isn’t a suitable jump in argument IMO.

[j2kun]

It's trivial because (when you say things like "high availability", which is not precise nor does it apply to CAP) you're ignoring the precision required for a valid proof.

[fjsolwmv]

Trivial is subjective. The sketch of the proof is simple, but you skipped the details and it's not obvious to everyone at first.