The Modern Approach to the Opening

In the 1970s and 1980s, Polugaevsky demonstrated

a new, modern approach to the opening: if you want to gain an advantage in critical variations, you have to take a risk, and play concretely and sharply, move by move. (Kasparov's My Great Predecessors III, p.105)

That sentence, which was italicized in the original, is the best summary of opening play that I have ever seen. It is self-explanatory, except perhaps for the phrase playing 'concretely', which is, as I understand it, the opposite of playing 'intuitively'. It means calculating everything, rather than relying on positional considerations.