C41 Philidor's Counter Gambit
François-André Danican Philidor (September 7, 1726 – August 31, 1795), often referred to as André Danican Philidor during his lifetime, was a French composer and chess player. He contributed to the early development of the opéra comique. He was also regarded as the best chess player of his age; his book Analyse du jeu des Échecs was considered a standard chess manual for at least a century, and a well-known opening and checkmate method are both named after him.
Andrew Soltis writes that Philidor "was the best player in the world for 50 years. In fact, he was probably about 200 rating points better than anyone else yet alive—set apart by the mysteries of the game he had solved."
Also interesting is GM Boris Alterman's opinion on Philidor play:
500 years ago chess was different from today. Pawns didn't cost as much as they do today. The best players started games with the gambits. Pawns were only a small price to: Open a file or diagonal; Create an immediate attack on an opponent's king. It was the Italian style of chess. All positions of the King's Gambit were very popular... The best chess player of his day was Francois Andre Danican-Philidor... His published chess strategy stood for a hundred years without significant addition or modification. He preached the value of a strong pawn center, an understanding of the relative value of the pieces, and correct pawn formations...
In the same web-article, Alterman also noticed, analyzing the game Count Bruehl–Philidor, F, 0–1, London 1783, that Philidor understood very well modern concepts like: power of passed pawns; bad and good pieces; space advantage; open files; pawn structure; importance of center.