The idea of this exchange is to create a weak Pawn on d5 against
which later on an attack can be instituted. However, it is very
doubtful whether the Pawn on d5 is really weak. Experience has
shown that Black wins just as many games as White in this
opening; the reason is probably that White, in order to open the
Queen's file for attack on d5, has to give away his center-Pawn
so that Black has more freedom for his pieces in the center.

(6) P-g3 Kt-c6
(7) B-g2 B-e6
(8) B-g5 B-e7
(9) o-o o-o
(10) Pxc5 Bxc5
(11) R-c1 B-e7
(12) Kt-d4 or Q-a4 followed by
R-f1-d1.

Instead of developing the King's Bishop to g2 White can just as
well play (6) B-g5 or f4, (7) P-e3 and (8) B-d3. In either case
the success depends rather on clever maneuvering in the middle-
game than on an advantage inherent to the opening.

What has been said of irregular replies which Black may try in
King's Pawn openings holds good in Queen's Pawn openings too.
There is no series of opening moves which needs to be memorized.
The principles of speedy development and of the maintenance of a
Pawn center lead the right way in all novel openings which a
player might try to avoid the well-known paths which have been
studied out by the masters of many generations.