Several carriers protect an item only to the extent that they can fail independently of one another, so spread each item across different households, ages and work groups, and keep a trainee learning it. Three carriers in one household are barely better than one, because a single fire or fever can remove all three, and two carriers taught by the same person share that person’s mistakes.
Part of Recording & Backup Systems
Carrier redundancy is the practice of holding each preserved item in several living people whose losses are unlikely to coincide.
Counting Carriers Is Not The Same As Counting Independence
The carrier article asks for at least three carriers in different households. The reason is probabilistic, and the probabilities show what the rule is really protecting against. The numbers below are assumptions to illustrate the method; replace them with what your community observes.
Worked Example: When Three Is Enough And When It Is Not
Assume each carrier has a 5% chance per year of being lost to the item (death, leaving, incapacity or forgetting), so q = 0.05, independently.
- One year, three independent carriers: all lost = q³ = 0.05 × 0.05 × 0.05 = 0.000125, or 0.0125%.
- Over five years without any new trainee: a carrier remains with probability 0.95⁵ = 0.774, so is lost with probability 1 − 0.774 = 0.226. All three lost = 0.226³ = 0.0116, about 1.2%. With only two carriers: 0.226² = 0.051, about 5.1%.
- Now put all three in one household and assume a 2% yearly chance of an event that removes the whole household (a fire, an epidemic in the house): P(all lost in a year) is at least 0.02, which is 0.02 ÷ 0.000125 = 160 times the independent figure.
So the independence of the carriers matters far more than the count. The same logic applies to knowledge taught by one teacher: if the teacher’s version is wrong, all their pupils are wrong together. Treat the teacher as a shared cause, not as an independent carrier (Verification & Version Control).
What You Need
- A carrier list for each canon item with household, age group, work group and who taught each
- A trainee for each item, a younger person learning it
- A schedule to retrain when a carrier is lost
- The register from Memory as Infrastructure
Method: Spread And Replace
Step 1: Count independent groups, not people. For each item, list distinct households, teachers and work groups.
Step 2: Aim for carriers in at least three independent groups. If the community has too few households for this, accept fewer and compensate with a stronger written reference.
Step 3: Mix ages. Include at least one younger carrier, who will outlast older ones, and not only the oldest.
Step 4: Vary the teacher. Have a new carrier learn from someone other than the existing carriers’ teacher, or have two teachers tell separately.
Step 5: Start a trainee when a carrier is lost, not when the last carrier is lost. Training takes time, and at three carriers, a lost one leaves two and no way to arbitrate disagreements by majority.
Step 6: Spread by place too. If the community splits or moves, each part should carry the canon.
Common Mistakes
- All the carriers are one family. A single illness or move takes the lot.
- All the carriers are elders. The age profile guarantees a simultaneous loss.
- Counting passive listeners. A person who heard an item once is a weak carrier; see the rehearsal ladder in Teaching Methods.
- Concentrating the canon in one gender, family or class. Distribute it. A group excluded from the canon will not keep it, and the knowledge is exposed to the group’s loss (Knowledge Preservation (governance)).
What’s Next
- Learn next: Verification & Version Control — what to do when the carriers disagree
- Combine with: Apprenticeship — training the next carriers by practice