As you point out, this isn't really the issue - the issue is accidental interference rather than deliberate trespass.

Encapsulation is mainly in existance to enforce clean boundaries between objects, and ideally these boundaries should be limited to a very small list of methods and few variables, such that changes in the objects don't break programs.

Furthermore, encapsulation can be broken with no access to variables, by virtue of having trivial getter/setter methods encapsulation IS broken, because the parameters of your object can be tweaked without asking the object nicely. Most folks already know this, but at least in the java world, many don't!

Deliberate trespass in your own codebase isn't something you fix in software, it's something you fix by going over to someone's cube and removing their mouse balls until they get the point.

I knew there was a reason I prefer optical mice.

Anyhow, if you can't trust your fellow coders to not play symbol table / reflection / etc type games, you have problems!

Well, preventing deliberate tresspassing can be an issue - if you run code of untrusted people. Don't think that never happens - it happens all the time. You don't want that processes can change their UIDs to anything they like, do you? ;-). Granted, Unix processes aren't very object like. Another example: MUDs runs code written by many untrusted contributors, sometimes hundreds or even thousands, who can subclass almost any object. A MUD would break down if there was no way to prevent deliberate tresspassing.

Furthermore, encapsulation can be broken with no access to variables, by virtue of having trivial getter/setter methods encapsulation IS broken, because the parameters of your object can be tweaked without asking the object nicely.

This I don't understand. How does that break encapsulation? The fact there are getter/setter methods means they are part of the API. Calling a setter method is asking the object nicely (and it's up to the object to refuse).

Abigail