For decentralized crypto-commerce to approach the richness of real-world commerce, we need similarly composable abstractions for cooperation under mutual suspicion. PL notions of “ownership” do capture much of the property rights notion of ownership. But trade of ownership rights under mutual suspicion also needs

• intermediaries, such as smart contracts running on blockchains, that can escrow the assets to enforce all-or-nothing bilateral exchange
• offer-safety, ensuring that each participant gets what they said they want, or gets a full refund of their escrowed rights.

But when the owned object is mutable, its tradable value can change with use, preventing the counterparty from getting what they said they want, violating offer-safety. We resolve this conflict by introducing “ownables”, a two-phase cycle alternating between using the owned object vs. offering it in trade.

Agoric’s Zoe framework enforces offer-safety even in the face of buggy or malicious contracts. Zoe currently supports higher-order composition of contracts in a limited manner. Folding ownables in on themselves, we explain how making some of Zoe’s key objects into ownables will enable richer higher-order composition under mutual suspicion.

Mark S. Miller is a pioneer of Agoric (market-based secure distributed) computing and smart contracts, main designer of the E distributed persistent object-capability programming language, inventor of Miller Columns, an architect of the Xanadu hypertext publishing system, an early cypherpunk, a representative to the EcmaScript committee, a former Google research scientist, a senior fellow of the Foresight Institute, and founder + Chief Scientist of Agoric.