Excerpted from Bogle on Mutual Funds by John C. Bogle, page vii

This book deals solely with mutual funds. It does not deal with the analysis and evaluation of individual stocks and bonds. In my view, attempting to build a lifetime investment program around the selection of a handful of individual securities is, for all the most exceptional investors, a fool's errand. To be sure, by owning individual equities, some active investors will inevitably enjoy spectacular results. But others perforce will lose much of their capital. Earning extraordinary returns from the ownership of individual stocks is a high-risk, long-shot bet for most investors. Specific stock bets should be made, if at all, in small portions, and more for the excitement of the game than for the profit. Serious money belongs elsewhere; it belongs in a widely diversified investment program. For nearly all investors, mutual funds are the most efficient method of achieving this diversification.