However, most people wouldn't consider "email" (SMTP) to be a blockchain, even if it's (sorta) decentralized.

But nearly every definition of blockchains does contain an append-only cryptographic log called a "merkle tree". Everything from there gets fairly vague.

This vaugeness leads to the joke: "blockchains are the 'cloud' of merkle trees". This refers to both the similarity to the hype and vagueness around the term "cloud", but with blockchains.

But git is a merkle tree. Is a signed git tree a blockchain? Well, yes and no...

"Blockchain" evolved to describe the space of "bitcoin-like-things". But the exploration space followed in its wake is large, and the evolutionary tree diverges dramatically.

This is similar to how "Roguelike" describes the space of "rogue-like-things", departing dramatically.

Thus you see people on here complaining about how blockchains will burn down the planet because of resource consumption, by which you mean "proof of work", which Bitcoin had.

But many newer "blockchains" use other mechanisms which don't chew planetary resources...

And so there's a disconnect. "I don't like roguelikes because I hate turn based games"... well, is Blazing Beaks a roguelike still?

"Blockchains are bad because they burn down the planet." But what about blockchains with proof-of-stake or a small permissioned quorum?

Since there's no agreement on whether PoW is essential (many might not even know an alternative), two sides arguing about things might actually be arguing about *different things*, thus "shouting past each other", which we do see on here all the time.

I think there's a good "shape" for what we might call a blockchain, but before we get to that, let's get to the other big argument that's happening on here: "blockchains" as an identity space... and a proxy war for other cultural dynamics!

"Blockchain bros": are they real? Yes. Is it everyone in the space? No, but it feels to most outsiders to be enough so that there's good reason for many to be put off.

It's even worse now that NFTs have polluted the space with people ignorant of what they're actually buying.

Side note: NFTs are not copyright, and actually I don't even think copyright (which bottoms out in state violence) is even a good *idea*, but people are being sold something which isn't what they're getting, and it's no wonder that people are mad about it.

That said, broad brush dismissals of this entire space as being white dudebros are *false*, and I have friends who are not dudes and not white who are hurt by broad-brush characterizations.

But on the other hand, don't use my words here to complain about "virtue signaling":

"Virtue signaling" is itself a virtue signal! It's like hipsters being the people who were most worried about hipsters a decade ago.

But "virtue signaling" is a thing everyone does because humans have limited time to assess, so yeah...

Let's get back to architecture again.

BLOCKCHAINS ARE NOT THE SAME AS DECENTRALIZATION

ActivityPub is a decentralized protocol, but it is not a blockchain.

However, it's another area in the space. Actually, there's *two different kinds*: "convergent decentralization" and "decentralized cooperating agents"

Almost all the focus of decentralization is in the "decentralized convergence", or sometimes if i'm smug, the "decentralized centralization" space. This is the world of blockchains and "quorums" (we'll come back to that)

Well *that's where the money is*! So... shocker!

However, most of the *important work* that needs to be done doesn't require a ledger, it's in the "decentralized cooperating agents" space. This is the realm of ActivityPub, the "actor model", and distributed capability-secure programming (CapTP!)

(It's also where my focus is.)

"Decentralized cooperating agents" work great with peer to peer systems... objects communicate with each other might cooperate despite being opaque to each other!

Surprised? Consider: you and I can cooperate without me reading your mind!

So: are blockchains essential to decentralization?

No! In fact, decentralized approaches dramatically predate Bitcoin! In fact, blockchains often lead to "reproducing" centralized structures because it's just too easy to "throw the centralized mindset on top of a blockchain"!

BUT! Does this mean that "decentralized convergence" and "decentralized cooperating agents" are at odds??

ALSO NO! I'm about to apply a *different* definition for "blockchain" and then let's think about how they might work together.

What if "blockchain" just meant "a single machine that many people run"?

The idea here is that a blockchain isn't a bunch of decentralized machines... it's a bunch of machines building *one unified abstract machine*. Useful for decentralized agreement on sequential operations.

Except we might actually want to split this up: there are "public" blockchains, like Bitcoin, Etherium, ZCash, and then there are smaller intentionally assembled sets where "here are the five participating machines, if three out of five agree this is the next action, then it is"