"Contrary to popular ways of understanding the stock market doesn't have causative powers as far as economic activity is concerned. It must be appreciated that the prices of stocks only reflect individuals'assessments regarding the facts of reality... While individuals can change their evaluations of the facts, they cannot alter the actual facts themselves ie. the facts which influence the future course of events."
Whether the stock market is a leading indicator of the economy is a question that can be answered by statistics ( it is a leading indicator, in fact the best single leading indicator ) and does not require an excursion into philosophy, unless of course the latter is required to justify one's world view.
IMO, when individuals change their evaluation of current facts, they not only sell/buy stocks at different prices, but change a huge range of other behaviors, and these latter changes do act as causes of future events.
The author forgets that the people who have the most influence over the money supply have portfolios of investments, too.
Only in the very strictest sense do I agree with the author on this point: No, the stock market isn't the cause. It is the best single measure of the causes. If the author thinks various money supply measures are better indicators, then that too could be argued with a statistical study.