[bzbarsky]

> to communicate their intention to collaborate on the plan

What the law says is "conspire to violate".

If person X and person Y together work out a way for person Y to commit murder and then person Y commits murder, is person X considered as conspiring?

> People don't think in groups

Sure they do. It's called "conversation" or "correspondence". If we had telepathy, we could skip the transcoding to sound or text, but we don't yet, but fundamentally it's the same thing.

[dragonwriter]

> Sure they do. It's called "conversation" or "correspondence"

Conversation is action, not thought.

> If we had telepathy

There's a couple different things (in fiction, naturally) that go by that name; the active analog to oral communication is also action, the sort of passive integration associated (not exclusively, just as an example) many hive-mind collective organisms in sci-fi is thought rather than action, but also not analogous to what goes on between humans.

[bzbarsky]

> Conversation is action, not thought.

I think the distinction here is a pretty dubious one. Consider, as a hypothetical, a situation in which one can actually tell "what someone else is thinking" based on a more advanced form of EEG. Would it still be "thought" as opposed to "conversation" if two people are doing it to each other simultaneously? Why is transcoding in terms of pixels on a monitor different from transcoding as sounds? Is the key difference for you whether the transcoding is active or passive on the part of the thinker of the thought?

Put another way, if we define "thought" as being limited to those things which have no perceptible effect on the world at all, then we run into the separate question about whether this "thought" thing exists in the first place.

[sowbug]

FWIW, the lawyers in this thread tuned out at this point. Nothing is very simple in law, but the ambiguities of criminal conspiracy are reasonably distant from the situation you've described. Conspiracy requires communication in order to agree to commit a crime. Positing a kind of thought that communicates doesn't really muddy the waters much.

I don't think the philosophers engaged, either. Redefining thought to be imperceptible denies everything we actually do know about the biological process of thought, so it's not clear the discussion leads anywhere worth going.