Mermelstein: Stock in undervalued companies will be worthless in a depression. Gold will be valuable. And no, I haven't noticed that the U.S. dollar has been sinking for 100 years. I'm not 100 years old. The U.S. dollar was strong until Nixon took us off the gold standard, though it had started its decline a few years earlier when inflation hit.
If U want to put all of your liquid assets in the stock market, that is your prerogative. Good luck.