That was a fun little shot, agip :)
I read it, completely--but I admit that I find it mystifying.
First, I would ask if Bogle's numbers are based on the SP500, or the entire US publicly-traded market. It is not specified, and could make a difference.
Second, I think some terms should be nailed down. From the shareholder perspective, "return on equities" = dividends + price change. Dividends are distributions to shareholders made at the discretion of the board. A share is a bundle of rights, one of which is the right to receive a portion of that distribution should it be made.
There is no debate that dividends contribute to overall return, as seen by a shareholder.
The other contribution, be it + or -, is from price change. Price change is defined as the difference between what you actually paid for a stock (i.e. how much you thought it was worth at the beginning of the time period, for whatever reasons), and what you could realistically sell it for (i.e. how much others think it's worth at the end of the time period, for whatever reasons).
I see nothing in the article that explains or even describes aggregate "reasons" for those who bought all the equities in question at the beginning of the time period, or any explanation or description of the aggregate "reasons" people would buy them at the end of the time period.
The hope for price appreciation is just that--hope. It is entirely speculative, unless you are doing insider trading, stock manipulation, or are big enough to move the market. The hope of price appreciation is always the hope that at some point in the future others will value things that they think are relevant to the stock price more than you valued the things that you thought relevant when you bought it.
It is hope, nothing more. It can be based on the strength of other investment vehicles, the strength of currencies, conflict, inflation, guesses about future performance for which one proxy is earnings growth, etc.
Different stock purchasers and sellers pay attention to different things. I see nothing in this article that describes the motivations for investor decisions.