Master Brain: a digital twin's knowledge base

The Master Brain is a digital twin's knowledge base: each twin's own brain, holding the materials the professional provides and their Book of Criteria. It keeps what the person knows and the rules they decide by, reviewed and approved by them, and it is what separates a twin from an avatar.

This article is part of Digital Twin by Legathum.

In short

Each twin has its own Master Brain: it shares a brain with no other.
It holds two things: the professional's materials and their Book of Criteria.
Rules come in to be reviewed and only count once the person approves them.
Before it works, the twin passes the Mirror Test.
The twin saying which rule each answer comes from is in development.

What a digital twin's Master Brain is

The Master Brain is a digital twin's knowledge base: the place where what the twin knows, and how it decides, is kept. The face and the voice are what you see and hear in a meeting. The brain is what answers.

Each professional digital twin has its own. A strategy consultant's brain is not mixed with a trainer's, or with that of another consultant in the same firm.

Without that brain, a twin would be an avatar with a generic model behind it: a familiar face answering with whatever seems plausible. With it, the twin answers with the knowledge and the judgement of one specific person.

What it holds today

A twin's Master Brain holds two different things, and each does its own job:

What a digital twin's Master Brain holds today
What it holds	What it is	What it is for	Who reviews it
Materials	Presentations, documents, articles or recordings the professional provides	Answering what something is or how it works	They are uploaded and consulted
Book of Criteria	Rules in plain language, each with its source	Knowing what the professional would do in a case	The person reviews and approves each rule

The materials say what the person knows. The Book says how they decide with what they know. A twin with plenty of materials and no rules explains well and decides badly.

The parts of a rule, and why each one carries its source, are on the Digital Twin blog: what a Book of Criteria is, and why every rule has a source.

What the Master Brain gets confused with

The name invites three mix-ups, and it helps to clear them before going on:

With a trained model. The Master Brain is a knowledge base the twin consults, and what is in it can be read and corrected.
With a script. A script says what to say in a conversation someone planned. The brain records how you decide in the ones nobody planned.
With the face and the voice. Those come from a single recording of about seven minutes and follow a separate path.

How knowledge gets in

Nothing reaches a twin's brain without going through the person. The path is this:

You provide your materials: what you already use to explain your work.
You write your decision rules, or draw them from cases you have already solved.
Each rule enters the Book as a rule to be reviewed.
You review it and approve it, one by one.
The Book is activated in a new version, with a note saying what has changed.

The Book in force can be exported whole, in a text format that opens in any editor. That is useful for reviewing it on paper or sharing it with a business partner.

How you check that the brain decides like you

With the Mirror Test. Real cases the person has already solved are given to the twin without the answer and compared blind. The twin only works if it agrees with the person in at least 90% of the cases and crosses no red line.

The test measures how the twin decides. A twin can look very much like someone and decide differently, and that is exactly what the test rules out before it talks to a client.

What exists today and what is in development

What exists today: each twin's own Master Brain, with the materials the professional provides; the Book of Criteria, with reviewed and approved rules, each with its source; face and voice from a single recording; consent by email with a video, the manual review and revocation with one click; the twin saying it is an AI the first time it speaks; the twin on Google Meet, Teams and Zoom, in more than 20 languages; and the Mirror Test before it works.

In development: the twin applying each rule in the conversation and saying which one each answer comes from; a record of the questions it could not answer, with a notice to the professional; memories and stories from the sessions; and exporting the whole brain, as well as the Book.

Also in development: each client's twin selling, scheduling, charging for and delivering their service from start to finish without the person stepping in. The 15-minute meetings with Legathum are taken by Deibson Silva in person.

What surrounds the brain

A brain with a person's judgement is only built with their permission. That is why four conditions go together:

Consent. In Spain, using a person's voice or image for commercial purposes requires their express consent (Organic Law 1/1982, Articles 2.2 and 7.6). At Legathum it is given by email, with a video, and the team reviews it by hand.
Revocation. Withdrawing consent must be as easy as giving it (GDPR, Article 7(3)). The twin is revoked with one click and stops talking at once.
Transparency. Anyone talking to the twin must be told they are dealing with an AI, from 2 August 2026 (EU AI Act, Article 50). The twin says so the first time it speaks, and its name ends in «Clon IA».
Real people only. There are no twins of invented characters.

These references are Spanish and EU law; other jurisdictions have their own rules.

A twin's Master Brain and a company's

The same idea exists at company scale. On the Legacy plan of the Legathum platform, the Master Brain is the company's institutional memory, with the company's own Book of Criteria, and the agents work on top of it. We cover it in what a Book of Criteria is and why your AI agents need one.

The difference is whose judgement it is. A twin's brain holds one person's. A company's holds that of the business, process by process, which is the work of company hybridisation with AI. For a consultant, the two come together in Legathum Legacy.

What to prepare before you have a twin

The brain can be started before anything is recorded. Three things move most of the work forward:

Gather the materials you already use to explain your method.
Write ten decision rules, each with its reason and the case it comes from.
Keep cases you have already solved, with what you decided. Those are the ones used for the Mirror Test.

If you are choosing between a twin and a video avatar, the comparison is in AI avatar vs digital twin.

Frequently asked questions

What is a digital twin's Master Brain?

It is the twin's brain: each twin's own knowledge base, holding the materials the professional provides and their Book of Criteria.

What does the Master Brain hold?

Today it holds two things: the professional's materials, such as presentations, documents, articles or recordings, and the Book of Criteria, with their reviewed and approved decision rules.

Does the twin learn from my conversations by itself?

No. What counts as your judgement is what you have reviewed and approved. Memories and stories from the sessions are in development.

Does each twin have its own brain?

Yes. Each twin has its own Master Brain, with that person's materials and rules.

How do you know the brain decides like me?

With the Mirror Test: the twin solves, blind, real cases you have already solved, and it only works if it agrees in at least 90% of them and crosses no red line.

Where are the digital twin plans?

The plans and their annual prices are on the plans page of Digital Twin by Legathum, with VAT added separately.

What a digital twin's Master Brain is and what it holds