In one of his films, Cary Grant arrived at his office, removed his jacket and his oxfords and slipped into a cardigan sweater and tassel loafers for the day. Years later, author Bruce Boyer wrote that the scene was the beginning of business casual.
I admit that his cardigan looked lighter and more comfortable than any suit jacket and I tried to emulate Mr. Grant one winter. I bought a gray Scottish cashmere version and brought it into the office with a pair of Alden tassel moccasins. But I was back to wearing my jacket and regular shoes after just a couple of weeks.
For one thing, the office was often a bit too warm for a sweater. And, more importantly, I discovered that it just took too long to change my shoes and a jacket every time I was going to lunch or a meeting, and back again when I returned. It's one thing to wear clothes and quite another to be dressing and undressing several extra times each day.
But the sweater was a worthwhile purchase overall as it serves me still. I wear it instead of a jacket for casual daytime entertaining on the weekend, with a pair of patterned trousers, an ecru silk shirt with a button down collar, slip-on shoes and a scarf.
The pictured John Laing of Scotland's classic cardigan model is from San Francisco's Cable Car Clothiers. These are rather steep at $595 but similar models are available from many reputable men's stores and online. One source that I've never tried is Brora Scottish Cashmere which has cardigans for £239.00 (about $400 ex VAT) . And I've seen them on sale elsewhere for half of that price.
Just remember that a cardigan should button, not zip. How else can a man leave the bottom button unbuttoned?