Every modern upgrade to wool is wool's job done worse, by oil, with a brand name on it. Fleece. What it is: polyester, the same stuff as the bottle. Why it exists: because wool is warm, and the bottle wanted the contract. Gore-Tex. What it is: a PTFE film, a forever chemical, glued to nylon. Why it exists: because wool shed rain and breathed for ten thousand years, and the film does both for about a season before it wets out. Thinsulate. What it is: polyester and polypropylene fluff with a trademark. Why it exists: because down and wool insulate, and oil needed a word. Moisture-wicking. What it is: a fibre that cannot absorb water at all. Why it exists: because wool takes in a third of its weight and still feels dry, polyester cannot, so the failure was renamed a feature. Odour-control base layers. What it is: polyester with silver sprayed on. Why it exists: because polyester stinks after four hours and wool does not, and the silver washes into the river by the third wash. Flame-retardant finish. What it is: a chemical bath, replaced every decade when the last one turns out to be carcinogenic. Why it exists: because polyester melts at 250 degrees and wool will not burn in ordinary air. Merino blend. What it is: half wool, half nylon. Why it exists: so the label can say merino and the price can say wool while the jumper is half plastic. Vegan wool. What it is: acrylic. Why it exists: because a sheep had to be left out of a jumper on principle, and the oil well was fine. Recycled polyester. What it is: the same plastic, from a bottle, shedding the same fibres. Why it exists: so the jumper can be sold as a good deed. Bamboo. What it is: viscose, which is wood pulp dissolved in carbon disulphide. Why it exists: because a plant on the label sells, and the factory downstream does not. Every one of those exists to add back a property wool came with, and every one adds a chemical, a smell, a fire or a plastic in the sea to do it. The sheep did the lot at once, on a hill, for grass, and the industry has spent eighty years selling you the parts.