Greek sea lenders forgave loans on sunken ships

In classical Greece a merchant voyage by sea was capital-intensive and genuinely likely to end in total loss — storms, piracy and primitive navigation meant a meaningful share of ships never completed their route. A standard loan, where the full principal plus interest is owed regardless of what happens to the borrower's business, made no sense for financing a voyage that could plausibly end with the ship, cargo and collateral all sitting on the seabed; no lender's ordinary terms matched the borrower's actual risk, and no borrower could realistically promise repayment no matter what happened.

Ordinary lending rates were also calibrated to loans where the borrower's ability to repay wasn't itself in serious doubt. A maritime voyage's real chance of catastrophic loss meant a normal interest rate wouldn't compensate a lender for the risk actually being taken, so the market needed a different instrument, not just a higher price on the same one.

Forgave the debt if the ship was lost, and charged higher interest on successful voyages, fusing financing and insurance into one contract.

Forgiving debt on a verifiable loss aligned the lender's claim with the borrower's actual ability to pay.

High interest on successful voyages compensated for the losses, making the portfolio profitable.

Fusing loss forgiveness and premium into one contract made voyages financeable that ordinary loans couldn't cover.

Price catastrophic failure into the contract itself: forgive debt on a verifiable trigger and charge a premium that covers the forgiven cases.

The structure let shipowners and merchants raise capital for voyages that would otherwise have been unfinanceable on ordinary lending terms, since no lender could rationally extend a standard loan against a venture with a real chance of total loss; the arrangement is documented directly in Demosthenes's own legal speeches concerning maritime loan disputes.