It is acknowledged that they spend many of the first years of their lives in acquiring a smattering of accomplishments; meanwhile strength of body and mind are sacrificed to libertine notions of beauty, to the desire of establishing themselves—the only way women can rise in the world—by marriage. (I.12)
Society's big focus on marriage tends to make women into superficial beings. After all, what can you expect when their only way of getting ahead is to marry a rich guy? Spending all of your time focusing on appearances and trying to look pretty doesn't make for a well-rounded human with a wide variety of interests, guys.
Let me reason with the supporters of this opinion who have any knowledge of human nature, do they imagine that marriage can eradicate the habitude of life? (2.33)
Wollstonecraft rejects the idea that marriage can somehow smooth out the conflict that exists between men and women. In Wollstonecraft's world, men are considered to be like masters and women are considered to be like servants. You can't fix something like that by slapping the word "marriage" on it and calling it love.
I will go still further, and advance, without dreaming of a paradox, that an unhappy marriage is often very advantageous to a family, and that the neglected wife is, in general, the best mother. (2.47)
Wollstonecraft believes that men are such tyrants to their wives that unhappy marriages can actually be better for a family than a happy one. In an unhappy marriage, a woman doesn't spend all her time trying to please her husband. Instead, she's forced to think for herself and to rely on her own resources, which makes her a better mother.
Of the same complexion is Dr. Gregory's advice respecting delicacy of sentiment, which he advises a woman not to acquire, if she have determined to marry. (2.50)
Dr. Gregory teaches his daughters to conceal any sentiment they might have if they plan on getting married. For him, women are only attractive to men if they are completely silent and pretty. Men don't want to confront the fact that women have inner lives.
To rise in the world, and have the liberty of running from pleasure to pleasure, they must marry advantageously, and to this object their time is sacrificed, and their persons often legally prostituted. (4.23)
Wollstonecraft is concerned about the way that women dedicate their entire lives to marrying up in society. This focus totally keeps them from ever becoming virtuous people, because their focus necessarily has to be on the superficial things they need to do to achieve their goals.
Still, highly as I respect marriage, as the foundation of almost every social virtue, I cannot avoid feeling the most likely compassion for those unfortunate females who are broken off from society, and by one error torn from all those affections and relationships that improve the heart and mind. (4.66)
Wollstonecraft wants her readers to know that she respects the institution of marriage. But she can't help but feel sorry for all of the women who have ruined their lives by marrying badly and committing themselves to horrible men.
Children, he truly observes, form a much more permanent connexion between married people than love. (5.54)
Wollstonecraft agrees that in many cases, children keep marriages together more than love does. But if this is the case, what happens once the children get old and move away? For Wollstonecraft, this is why there needs to be true friendship and mutual respect between a husband and wife.
In the choice of a husband, they should not be led astray by the qualities of a lover—for a lover the husband, even supposing him to be wise and virtuous, cannot long remain. (6.14)
Wollstonecraft warns women against marrying for love, since she doesn't believe that love (at least the sexual kind) can last more than a year. For her, only respect for a person's mind can sustain a marriage in the long run.
To say the truth women are, in general, too familiar with each other, which leads to that gross degree of familiarity that so frequently renders the marriage state unhappy. (7.24)
Wollstonecraft hates the fact that women can't be friends with men, since she feels that too much friendship between women can actually lead to horrible things. She's a little bit vague on what these horrible things are, but oh well. That just gives us lots of room to speculate.
But in order to render their private virtue a public benefit, they must have a civil existence in the state, married or single. (9.28)
Wollstonecraft insists that if women are going to have a positive impact on the world, they need to have some sort of presence in the public sphere, whether married or single. They can't just keep spending their whole lives being wives or spinsters and nothing else.