Fleece's Achilles' heel is that, without a nylon coating, it lacks any wind resistance--a slight breeze that wool and cotton would turn back cuts right through fleece with a nasty bite.
A person who wears fleece will get cold easily. 
mnli hypothesis: A person who wears fleece will get cold easily.  premise: Fleece's Achilles' heel is that, without a nylon coating, it lacks any wind resistance--a slight breeze that wool and cotton would turn back cuts right through fleece with a nasty bite.