The Merchant's Trade

A merchant arranged a complex trade: he would sell grain to a baker, use the proceeds to buy wool, and trade the wool for dye.

He sold the grain. He bought the wool. But the dye merchant had sold out.

Now he held wool he didn't want and no dye to show for it.

A wiser merchant would have made each step reversible. Sell the grain, but keep an option to buy it back. Buy the wool, but only if the dye is confirmed.

Each step forward must have a path back.