A recent article in Forbes describes the late John Bogle as “dogmatic and rigid” and a “sanctimonious scold.” But, it adds, “he was right.”

Referring to Bogle as the “titan of low-cost investing,” the article offers an overview of his long and fascinating career and his consistent preaching that investing costs matter, more than past performance.

Bogle’s thesis—that if you hire a money manager to beat the market (paying fees whether or not they do)—eventually your luck will run out and you will be “overtaken by the law of averages.” It’s tough for even top-performing funds to beat indexing over a long period, he argued.

When Bogle founded Vanguard in 1976 to create the first retail index fund, the article reports, it was a “sales flop,” since investors were not inclined to sign up for a guaranty of mediocre returns. Decades later, however, “Wall Street recognized that he was onto something.”

Bogle took on the Efficient Market Hypothesis with what he called the Cost Matters Hypothesis, which the article explains this way: “It costs money to try to beat the market. When a group of people do that, some will win, some will lose, but collectively they will get the market’s return—before fees. After fees, they will get much less.” The article contends that “Jack Bogle’s religion is saving investors something like $100 billion a year.”