Chapter 7 (1) P-d4 P-c5

(2) P-e3

With Pxc5 White would give away his center-Pawn, and Black would regain the Gambit-Pawn easily after (2) ..., P-e6. White could play (2) P-d5, thereby depriving Black's Queen's Knight of his best developing square. But in doing so he would lose time with a Pawn move which does not improve the mobility of his own pieces, and consequently (2) P-e3 is preferable.