The three roads, in plain words

What are we doing here.

§Three verbs, nothing else

Stand outside the machine — a browser, another program, a script — and there are exactly three things you are allowed to ask it:

1. "Tell me about yourself." What sessions exist, what shelf of study methods is available, what seats a Cell could be opened from, how this session relates to others. Nothing here changes anything; it is all lookups.
2. "Here is something new." A person's opening question, an answer typed into a form, the single word that means "attest this." Every single change the machine ever makes to what it knows arrives through this one road, always as a named kind of change — never as an anonymous blob.
3. "Show me a computed view." What is on the sheet right now, what a particular Cell's lifecycle looks like, what a given tuple's whole neighbourhood in the log is. Always a read; never, whatever it looks like on screen, a second copy of the truth living anywhere but the log itself.

That is the entire outward-facing surface of the system. Every button described anywhere in this book — Commit, Ask the world, Open a Cell, Attest, Pin — is, underneath, one call down one of these three roads, with a name attached saying exactly which kind of thing it is doing.

§Why this is worth its own part of the book

Because it means learning "what can this system be made to do" is a genuinely finite, listable task — not a matter of discovering emergent behaviour by trial and error. 5.3 simply lists everything currently on offer down road two and road three, in full, because a list that short is actually worth reading whole rather than sampling.

§A road for asking, a road for telling, a road for showing — never mixed

Nothing on the "tell me something new" road can ever silently double as a way of reading something back, and nothing on the "show me a view" road can ever have a side effect. This separation is not a style preference; it is load-bearing for everything the rest of the book relies on — Part 1's claim that the log is the one truth only holds if there is genuinely no other channel by which something could quietly change it, and Part 6.2's formation boundary depends on "show me a view" being, provably, incapable of writing anything back.