MORE THAN TWO MONTHS

ago, on April 4, I told you to

. Now I have the opposite message: It's time to buy.

After several years of comparative calm, and a 2005 that bordered on dull, the market has dished up both selling and buying opportunities with almost dizzying speed, all thanks to fast-rising volatility.

What changed in such a short time to bring down the curtain on the near-euphoria of April and early May? As I noted back then, the rally never made much sense to me. But many financial journalists were so eager to proclaim a new record close for the Dow Jones Industrial Average (and had obviously already written their stories) that they went ahead and ran them even before the Dow crossed the magic threshold. The major averages have been plunging ever since.

Before I address the fundamentals, let me remind readers, especially newcomers to Common Sense, that why the market has plunged below a new buying target is less important than the fact that it has. The Common Sense discipline is to buy lower and sell higher. I buy at intervals of 10% declines in the Nasdaq, and sell at intervals of 25% gains, the median decline and rise in bear and bull markets. Thus, I urged you to sell in April, when the Nasdaq hit 2365, a 25% rise from my last selling target.

This system doesn't aim to identify precise market tops and bottoms, which I don't believe to be possible. Yet once again, that selling target came very close to a market peak. I don't expect this streak of precision to continue, but it has nonetheless reinforced my belief in the importance of a system that helps take the emotions out of buying. Many people thought I was crazy to sell in April. Now no one wants to buy, not with some overseas markets dropping 10% in a day and the Dow in a seemingly relentless decline.

While the Nasdaq dropped convincingly below the buying target of 2138 in Monday's global selloff, it had actually crossed the buying threshold last Thursday. I noticed the sharp drop with considerable interest that day as I was heading out to lunch with a colleague. Did I delay my departure to stay glued to the computer screen or start sending in buy orders? Absolutely not. Another fundamental principle of this column is that it's written for people who aren't professional traders and otherwise have busy lives and careers. I have never missed a lunch because of the stock market and I'm not going to now.

By the time I returned, the market had reversed course and was above the target. I worried briefly that I had missed an opportunity, but then shrugged and went about my work. This is another principle of Common Sense investing: There's always another opportunity sooner or later.

Which brings us to this week's selloff, which has brought the Nasdaq deep into buying range. To listen to the many Wall Street pundits calling for the scalp of Fed Chairman Ben Bernanke, he's to blame, for flip-flopping over the issue of future interest-rate increases. First he talked about a "pause," which Wall Street interpreted as a halt. Then he had to clarify that in an encounter with CNBC anchor Maria Bartiromo at the White House Correspondents dinner, a distinctly undignified setting for major policy pronouncements. Finally, he poured fuel on the fire last week with tough talk on inflation. Another rate hike late this month now seems all but certain.

No wonder Bernanke has appointed a committee to study the issue of communication. But wording aside, is there really anything so startling about the prospect of another quarter- or half-point rise in rates? Why investors across the globe have suddenly awakened to the fact that the post-Sept. 11 glut of cheap capital is coming to an end mystifies me, when this has seemed apparent for well over a year. But better late to the realization than never. Bernanke's mission isn't to win popularity contests, but to do what's right in the long term. Wringing out inflation expectations, however painful for some in the short term, should reap long-term benefits.

I like buying opportunities such as these, which seem more emotional than rational. After the post-Sept. 11 and post-Internet bubble fragility, both the U.S. and global economies seem healthy, which makes this a good time to tighten interest rate policy, not to mention a good time to buy stocks. If you've been reading this column, you should be well prepared for rising rates and should have a shopping list for stocks ready. (I'll also be examining some promising stocks and sectors in the next few weeks.) If you have nothing specific in mind right now, buy a broad index fund or ETF. You can always diversify later.

Will the market go down even further? Quite possibly. As usual, I make no predictions, and I'm not trying to call a bottom. All I can say with certainty is that stocks are much cheaper now than they were two months ago.