OK, I'm only going to do this once.
Tax cuts make everyones stuff more valuable. If you own a business and receive a real tax cut, an income tax cut and a capital gains cut, the stuff you own becomes more valuable to you. So then most business people will now go out and buy and sell more of the stuff because they get mo' money from it net after tax. There's more activity, people take money out of their savings and/or will go to the bank or investors for more capital because they can put that capital to work buying and selling the stuff that just became more valuable. Then they have to hire more people to find more stuff and keep track of the stuff they already own.
Tax cuts BOOST the economy because everybody's stuff is more valuable. As the economy grows the gubbamint collects more revenue from the additional activity.
Vote for me in 2012 and I'll make your stuff more valuable