How does Capulet respond to Paris' proposal to marry Juliet?

Early in the play, in Act I, Scene 2, Lord Capulet sends mixed messages to Count Paris about the availability of his daughter Juliet to be married. At first he insists that Juliet is too young and suggests that Paris wait two years, saying, "Let two more summers wither in their pride/Ere we may think her ripe to be a bride." After all, Juliet is only thirteen years old. Paris, however, claims that even younger girls have already given birth ("Younger than she are happy mothers made"). Capulet then seems to soften his stance, telling Paris that he might be willing to approve of such a marriage only if Paris can win Juliet's heart. He asserts that her happiness is utmost in his mind. He says,

But woo her, gentle Paris, get her heart;
My will to her consent is but a part.
And, she agreed, within her scope of choice
Lies my consent and fair according voice.

Later in the play, in Act III, Scene 4, Capulet totally changes his mind. He is swayed by the death of Tybalt and the atmosphere of sorrow which pervades his household. He wrongly believes that Juliet is distraught over her cousin's death and hopes to plan a "day of joy" to cheer her up. He must have believed that Paris was a good match for Juliet and so agrees to hold the wedding as soon as possible. He also seems to do an about face about Juliet's approval of the marriage because he savagely berates her when she disagrees with his arrangement at the close of Act III.