For example, if two untrusted parties traded a service and then at some point the seller called in payment of the resulting account but the buyer was unable to come up with the money at that point in time, the loss of that failure would be temporarily distributed amongst his trust group. This way his rating in the financial dimension of trust is maintained, but has the potential to drop within the context of his own trust group if he can't repay his members in accord with their own internal agreements. If he were continually badly behaved he may be rejected from his trust group, and then his trust rating would be affected making it more difficult to become a member in other trust groups.
Having assurance as the foundation allows individuals to only be required to form contracts with those they know and trust, and it's based on supporting our peers when they're unable to meet their obligations, rather than treating contracts as rules involving punishments for violations. In such a system, obligations solidly met because people don't want to let down those they're closely associated with.
Such agreements allow the creation of assurances which can then act as axioms for functionality on higher levels of abstraction in the system. Sets of simple agreements between members of trust groups can also form a foundation for alignment with the common vision.
Initially, "Policies of Assurance" grew out of The Doctrine of Contribution and General Average, which is found in the Codes of the ancient Rhodians. In the Platform network, the cost of failure to meet obligations can be distributed amongst the members of a trust group allowing it to exhibit a higher level of trust than any of the individual members have alone.
Foundation of assurance in the Platform specification
The Platform specification inherits some default member contracts deriving from the common vision and the values. In a Platform, these contracts are documents that members can agree to by sending a signed secure email containing the contract text and a confirmation of comprehension and agreement to a number of other peers who then sign and return the message with a confirmation of having witnessed the signed agreement.