What if everyone in the world, right now, could produce supersmallpox or craft a nuke (or, given sufficiently-advanced technology, do something else for which the same technology offers a poor defense compared to the offense)?

Wouldn't the only chance for survival entail a daily, warranted scan by the thought reader of everyone to ensure nobody was tempted to do it? (Or, better, omniscient surveillance.)

The point here being that the "1984" route is a valid (if not ultimately preferable) choice in this philosophical fork in the road.

(Also, rest unassured, I hate having this opinion.)

Interesting question. I think this would probably be protected against by the fifth amendment, would it not?

What if the communication were stored on a digital device, embedded in a person's skull, which they were able to interface their brain with?

That may sound like an unrealistic scenario, but there are already people with medical implants that record digital data, and there has been a case of using Fitbit data to help convict someone:

https://www.nytimes.com/2018/10/03/us/fitbit-murder-arrest.h...

Interesting question yourself. I am not a lawyer, but: I think this would hinge on the definitions of "compelled" and "witness" in the fifth amendment. I think the courts would rule that being "a witness against himself" would require synthesizing thoughts into a statement then made under oath. I think searching thoughts would be considered a search.

It would be interesting to see how the courts would handle the fact that many thoughts are fleeting and not indicative of belief or intent.

It might also be allowed by the fourth amendment, provided the warrant was legitimate, depending on the interpretation of "in their persons."