The video above, from Elizabeth Warren’s campaign tour in Massachusetts, has been circulating online. And if you haven’t watched it yet, you should.

One worry about Warren, the Harvard Law School professor challenging incumbent Republican Senator Scott Brown, is that she won’t be able to connect with average voters. As you’ll see, that very plainly that is not the case. But pay close attention to what she says about progressive taxation, starting at about 50 seconds into the video:

I hear all this, you know, “Well, this is class warfare, this is whatever.”—No! There is nobody in this country who got rich on his own. Nobody. You built a factory out there—good for you! But I want to be clear. You moved your goods to market on the roads the rest of us paid for. You hired workers the rest of us paid to educate. You were safe in your factory because of police forces and fire forces that the rest of us paid for. You didn’t have to worry that marauding bands would come and seize everything at your factory, and hire someone to protect against this, because of the work the rest of us did.
Now look, you built a factory and it turned into something terrific, or a great idea—God bless. Keep a big hunk of it. But part of the underlying social contract is you take a hunk of that and pay forward for the next kid who comes along.

These days, when you hear Democrats defend proposals to raise taxes on the wealthy, usually they argue about the numbers. We need more revenue in order to maintain vital government services, those who can afford to pay more should pay more, etc. And that’s fine as far as it goes.

But there’s also a philosophical rationale for progressive taxation. Two, actually.

One is the role that luck plays in life. As I wrote a few weeks ago:

Almost by definition, people who are successful have benefited from some measure of good fortune. That fortune can take the form of obvious, material advantages--like access to advanced technology and good schools. Or it can take the form of more subtle, but still important, assets for moving forward in life--like good health or loving parents.
Yes, a good work ethic will take you far. And I know many well-educated professionals convinced that nobody works as hard as they do. (I’ve been known to indulge the thought myself.) But I’ve met many people at the bottom of the income ladder who work just as hard, for far less reward. Between 1980 and 2005, the richest 1 percent of Americans got more than four-fifths of the country's income gains. Does anybody seriously believe that the other 99 percent didn't deserve to take home a much larger share?

The other argument is the one Warren makes in this video: Every person’s success is a product, in part, of investments that Americans made, collectively, going back generations. As she says, it was the taxpayers who paid for the schools, the roads, the scientific research, the first-responders, and all sorts of other public goods on which every business – and, indeed, every American – depends. Those who benefit the most from these investments don’t merely have the ability to pay more for them. They have an obligation.

And this argument isn’t simply about taxation. It’s also an argument for making more of these investments going forward. It’s worth spending government money on infrastructure, schools, and other public goods – even if it means paying for them, eventually, with higher taxes – because we all stand to benefit from them.

To echo Steve Benen and Greg Sargent, Warren’s candidacy is one of the most exciting political developments of recent months – and not simply because of what it means for Massachusetts.