“I don’t really know how to do casual clothes,” remarked Oscar de la Renta to WWD in 1979. “It looks contrived when I do it.” That bit of self-assessment may well be true, but it certainly hasn’t hurt the designer’s career a bit. After all, de la Renta’s dedicated and ever-growing clientele doesn’t look to him for an ensemble in which to take the kids to soccer practice. Since Day One, Oscar’s woman has been one who dresses elegantly for both day and evening. Much like the man himself, his collections are never short on charm, life or color, yet they are unyieldingly well-mannered, never vulgar. And whether he’s working with the uptown propriety of a tidy lunch suit or the haute bohemia of a crystal-encrusted caftan, he never fails to weave in a dreamy thread of magic. Here, some great moments from de la Renta’s fabulous 40 years of fashion.