Kunal Kapoor: I remember Jack for many, many reasons, but most of all for his optimism and the fact that he really believed in helping the small investor and ensuring that that investor could have that great outcome that he or she was looking for.

Christine Benz: You could obviously fill books about Mr. Bogle's contributions to the financial services industry and to individual investors. I consider it one of the great privileges of my career that I got to meet Mr. Bogle through our annual Bogleheads Conference conversations. We would do video interviews. And I'll also say that as a young analyst reading Mr. Bogle, getting to know his philosophy was enormously clarifying to me as a young analyst. It helped shape the types of products that I would recommend, and also helped shape my career path. He was pro low-cost products of course, but he was also against so much of the complicated gobbledygook that Wall Street puts out. Hearing his philosophy was an incredible gift.

Ben Johnson: I don't believe that there has ever been, nor will there ever be, anyone who has given more to investors and taken less in return than Jack Bogle.

Jeff Ptak: His premise was the more that we can save investors, the more that ends up in their pockets, the better the outcomes they achieve. The fact that we now see millions of investors that are in index funds, including Vanguard index funds, I think stands as a towering monument to his legacy. It's immeasurable in the sense that Jack really changed the psychology of investing. His ethic was that you put the investor front and center where they belong. They don't subordinate to other business interests.

Instead you win when they win. That was not conventional wisdom in the industry some years ago when he was trying to popularize indexing and bring Vanguard up, and yet he inverted the psychology of the industry. He enshrined a new standard that put the investor front and center. I think we owe a lot to Jack, because now we see that sort of ethic, that sort of standard being table stakes in the industry. I think that all investors--not just Vanguard investors--all investors are better off for Jack's efforts. He's had an enormous impact, both in measurable and immeasurable ways.

Laura Lutton: One of the things that's so impressive about Jack Bogle was his unrelenting focus on the end investor, and he maintained that focus despite serious health issues and dust-ups along the way with other executives at Vanguard and so forth. I think when we look at the impact that he's had across his life, it's really tremendous, and we all have him to thank for that.

Alec Lucas: He didn't just pioneer the first index fund. He helped investors in all kinds of ways that get less recognition. He pioneered closure of funds to help protect current shareholders. He was an advocate in simplifying the language of prospectuses so that your average investor could understand them and make intelligent choices. He was a tireless advocate for others, and he will be sorely missed.