Aside from Lee's and Longstreet's disagreement about battle tactics--Lee prefers an offensive strategy with frontal assaults by massed forces, while Longstreet believes that a defensive posture is the best chance for success--they also have opposing moral views. Lee is a member of Virginia's aristocracy (his father was Light-Horse Harry Lee, a former Revolutionary War hero and governor; his wife is the granddaughter of the first First Lady, Martha Washington), and his loyalty lies with the state. He sided with the Confederacy only after Virginia seceded, and Lee could never envision fighting against his state. Longstreet, on the other hand, is not a Virginian, nor does he believe as strongly in the Confederacy. Longstreet has more on his mind than battle; his family has been decimated (he lost three children to disease the year before), and he is weary of the death that surrounds him, knowing that his corps will be facing many of his old comrades from the old pre-war army.
Additionally, Lee views the war as a religious battle in which God sides with the Confederacy, a belief held by his late commander, Stonewall Jackson. Longstreet is a more practical man and far less religious: When Lee tells Longstreet that the desperate attack on the third day "is all in the hands of God," Longstreet recognizes that faith alone will not win this battle and that it is Lee, not God "that is sending those men up that hill." He begs Lee to reconsider, still hoping for a strategic withdrawal and defensive counter-march on the next day, but Lee believes that victory is a fate destined for the South.