The second major category of investments involves assets that will never produce anything, but that are purchased in the buyer's hope that someone else -- who also knows that the assets will be forever unproductive -- will pay more for them in the future. Tulips, of all things, briefly became a favorite of such buyers in the 17th century.

This type of investment requires an expanding pool of buyers, who, in turn, are enticed because they believe the buying pool will expand still further. Owners are not inspired by what the asset itself can produce -- it will remain lifeless forever -- but rather by the belief that others will desire it even more avidly in the future.

The major asset in this category is gold, currently a huge favorite of investors who fear almost all other assets, especially paper money (of whose value, as noted, they are right to be fearful). Gold, however, has two significant shortcomings, being neither of much use nor procreative. True, gold has some industrial and decorative utility, but the demand for these purposes is both limited and incapable of soaking up new production. Meanwhile, if you own one ounce of gold for an eternity, you will still own one ounce at its end.

What motivates most gold purchasers is their belief that the ranks of the fearful will grow. During the past decade that belief has proved correct. Beyond that, the rising price has on its own generated additional buying enthusiasm, attracting purchasers who see the rise as validating an investment thesis. As "bandwagon" investors join any party, they create their own truth -- for a while.

Over the past 15 years, both Internet stocks and houses have demonstrated the extraordinary excesses that can be created by combining an initially sensible thesis with well-publicized rising prices. In these bubbles, an army of originally skeptical investors succumbed to the "proof " delivered by the market, and the pool of buyers -- for a time -- expanded sufficiently to keep the bandwagon rolling. But bubbles blown large enough inevitably pop. And then the old proverb is confirmed once again: "What the wise man does in the beginning, the fool does in the end."

Today the world's gold stock is about 170,000 metric tons. If all of this gold were melded together, it would form a cube of about 68 feet per side. (Picture it fitting comfortably within a baseball infield.) At $1,750 per ounce -- gold's price as I write this -- its value would be about $9.6 trillion. Call this cube pile A.

Let's now create a pile B costing an equal amount. For that, we could buy all U.S. cropland (400 million acres with output of about $200 billion annually), plus 16 Exxon Mobils (the world's most profitable company, one earning more than $40 billion annually). After these purchases, we would have about $1 trillion left over for walking-around money (no sense feeling strapped after this buying binge). Can you imagine an investor with $9.6 trillion selecting pile A over pile B?

Beyond the staggering valuation given the existing stock of gold, current prices make today's annual production of gold command about $160 billion. Buyers -- whether jewelry and industrial users, frightened individuals, or speculators -- must continually absorb this additional supply to merely maintain an equilibrium at present prices.

A century from now the 400 million acres of farmland will have produced staggering amounts of corn, wheat, cotton, and other crops -- and will continue to produce that valuable bounty, whatever the currency may be. Exxon Mobil (XOM) will probably have delivered trillions of dollars in dividends to its owners and will also hold assets worth many more trillions (and, remember, you get 16 Exxons). The 170,000 tons of gold will be unchanged in size and still incapable of producing anything. You can fondle the cube, but it will not respond.

Admittedly, when people a century from now are fearful, it's likely many will still rush to gold. I'm confident, however, that the $9.6 trillion current valuation of pile A will compound over the century at a rate far inferior to that achieved by pile B.

Our first two categories enjoy maximum popularity at peaks of fear: Terror over economic collapse drives individuals to currency-based assets, most particularly U.S. obligations, and fear of currency collapse fosters movement to sterile assets such as gold. We heard "cash is king" in late 2008, just when cash should have been deployed rather than held. Similarly, we heard "cash is trash" in the early 1980s just when fixed-dollar investments were at their most attractive level in memory. On those occasions, investors who required a supportive crowd paid dearly for that comfort.

David Fuller's view We can expect gold bugs to attack this view over the next few months, and not without some justification.

For instance, while that hypothetical "cube of gold" will still be around a century from now, albeit held by many investors and central banks around the world, can we be certain that Exxon Mobil will continue to flourish and that America's farmland will remain equally productive?

I certainly hope so but there are no guarantees.

Where Mr Buffett's critics will be on firmer ground is in pointing out that he did not buy gold in 2001, when it was dirt cheap and fiat money printing was accelerating. Gold has handsomely outperformed the Oracle of Omaha's or anyone else's equity portfolios subsequently, including dividends paid. Timing is everything.

Where I think Mr Buffett's equity strategy could give gold a run for its money is over the next decade or two. I say this even though inflationary pressures could increase substantially during that period in response to all the fiat currency that is still being created.

My point is - gold at $1750 is obviously not the bargain that it was at £250.

Mr Buffett's strongest argument, I believe, is in his opening comments comparing bonds, bank deposits and money market funds unfavourably with the long-term outlook for equities.