The rights and involved duties of mankind considered
If we're going to make a solid argument for anything, Wollstonecraft says, we need to begin at the very beginning at look at our most basic assumptions.
Her first (and most important) assumption is that the power of Reason (and Reason alone) is what places humankind above the rest of the natural world.
Her second biggest assumption is that virtue and moral goodness are what make one human being better than another.
Her third and final assumption is that God gave us passions and temptations so that we could gain knowledge by struggling against them. Therefore, the qualities of Reason, Virtue, and Knowledge are our starting points.
Reason is supposed to help us overcome our prejudices by looking at things more objectively. Unfortunately, most men use reason to justify prejudices instead of overcoming them.
Europe is especially bad when it comes to prejudices.
A quick look at the society of Wollstonecraft's time would show you an irrational and unfair world, where a small group of people was rich and powerful simply because they'd been born into the right family (like kings, queens, and other royalty). This is the very reason why people were trying to agitate for democracy all over the world while Wollstonecraft was writing Vindication.
Wollstonecraft mentions Jean Jacques Rousseau as an example of someone who became so fed up with the injustice of the modern world that he turned away from it and lived in solitude. Pay attention to this part of the book, because Wollstonecraft is going to have lots to say about Rousseau as we go on.
Wollstonecraft disagrees with Rousseau's belief that humans should return to their natural state and start acting more like animals again. She insists that God gave humanity reason and civilization in order to improve life, though she admits that many humans have abused these gifts.
Wollstonecraft doesn't just disagree with tyranny in government. She also disagrees with any part of life where one person demands blind obedience from another. That includes schools and workplaces. In other words, a teacher or a boss always needs to be able to justify their decisions to their students and workers. As you can imagine, there are a lot of teachers and bosses out there who don't feel the same way.
At the end of the day, every human being should have the power to question the decisions of another human being on rational grounds. It is never okay for one person to tell another: that's just the way it is, so do what you're told.
Wollstonecraft suspects that in the early days of humanity, the biggest and strongest people tended to rule over the others. But now we've evolved into the age of reason, which means that brute strength is no longer a valid basis for power. People need to get people to agree with them through rational arguments.