“It’s happened before,” he said. “I’ll be all right. And now, what can I do for you?”

We talked at length, and his voice got stronger as he launched into a lecture on “the relentless rules of arithmetic” for mutual funds. He said they amounted to this: The fees charged by brokerages, fund companies and advisers were sapping the returns of millions of hard-working people who were trying to save for retirement. Reduce the fees and give the money to the people who need it, he said. That, he said, was what his career was all about.

After a few minutes, he faltered, and we agreed to resume the conversation a week or two later. Jack asked me not to reveal that stretch of weakness and hospitalization — or other bouts that occurred later — and I didn’t, while he was alive.

Now, after the announcement of his death on Wednesday, I believe it’s fair to let people know how strong he was, and how idealistic.

[Read the obituary of Mr. Bogle.]

The basic biographical details are well known. A poor boy and a brilliant student, he discovered an interest in asset management — and the burden of fees on investors — while an undergraduate at Princeton. He had his ups and downs in the fund business but made history by popularizing the index fund and creating Vanguard, giving up his chance at great wealth by eschewing ownership of the company.

The Vanguard Group, as he structured it, was owned by its mutual funds, which were owned, in turn, by fund shareholders and dedicated to low-cost investing. He was paid well and accrued what would be a great fortune for most of us — he told me last year his assets were “well below $100 million” — but it’s small change by the standards of money management.