Objects can be considered a bad idea on their face, because they are made up of code wrapped tightly around state variables that are supposed to be secret and hidden. The functional style preaches the exact opposite: functions should not have side effects; all their state is either passed-in or returned. The more state your program keeps, and the greater the number of types of transitions that are possible, the greater the number of ways that the overall state can become inconsistent and cause an error. The way to keep the problem in check is to try to make state and state transitions simple and clear. I'm not a functional absolutist -- I don't use functional languages very often, and I see nothing wrong with doing simple things in the most natural style and language -- but I think the point is valid about how to deal with state.