Elon Musk blasted one of Warren Buffett’s primary investing tenets earlier this week when he said during his Tesla TSLA, -9.88% analyst call that “moats are lame” and “if your only defense against invading armies is a moat, you will not last long.”

The classic definition of a moat is, of course, a body of water protecting a castle. In Buffett terms, it’s the advantage certain companies hold over the competition due to by having a powerful brand that creates high barriers to entry.