Almost a quarter-century ago, I spotted two brothers named Tom and David Gardner on AOL (when it was pretty much the only way for most of us to do anything online). They were the guys behind The Motley Fool, and their mission was to teach people how to become informed investors. This was at a time when buying stocks and mutual funds was supposed to be done only by professional brokers and big institutions. Not only were the Gardners writing about investing, they were also opening up forums for the public to share their thoughts on companies they liked or loathed.

Over the next few years, I not only got to know David and Tom, but also had them on my radio show many times (I even helped them put together the pilot for their own radio show). Now, more than 20 years later, I still subscribe to one of their services, and the Motley Fool thrives online and in podcasts and in print. They’ve just published the third edition of their bestselling book, “The Motley Fool Investment Guide,” and I was happy to talk with David about it.

We discussed how investing is different than it was in the earliest days of the Motley Fool, what he says to naysayers about the bull market, and what advice he offers people in retirement or nearing that age who wonder what to do with their money. We also talked about disrupters, those companies that have changed the way the world works, and whether it’s still worth investing in big names like Amazon, Facebook, and Netflix. Finally, I asked David why, after recommending so many tech stocks like eBay and PayPal, he is now suggesting buying 3M, the company that makes Post-Its.

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