Does this bull have the brawn to keep running?

What a difference a few weeks make. After fretting over the fate of Eastern Ukraine, the wintertime economic slowdown and even the spread of the MERS infection, the optimists have taken control of the market and pushed the S&P 500 index firmly above the 1,900 level for the first time ever.

It's an impressive show of force, and it could represent a breakout from the sideways doldrums that the index has been mired in since March.

But it's not perfect: Volume and breadth has been lackluster as trading activity remains light and buying interest narrow. Moreover, small-cap stocks continue to lag behind, and buying interest remains curiously high in the U.S. Treasury bond market -- suggesting some apprehension among bond traders.

The big question is: Will the stock rally continue?

It's being driven primarily by a turnaround in biotechnology, an area that had been hit hard with selling pressure after peaking in late February into a low in mid-April. The Biotech iShares (IBB) lost nearly 25 percent over this period. But over the last few days, the IBB has been on a tear, up more than 5 percent -- outpacing the S&P 500's gains -- as bargain hunters have moved in and forced short sellers to cover their positions.

And we've also seen a big drop in the market's sense of nervousness.

The fact Ukraine's presidential election went off largely without a hitch over the weekend helped. But investors are becoming increasingly numb to headlines that would've recently caused much consternation. Such as reports that the Japanese central bank is starting to look at ways to roll back its cheap money stimulus program. Or that the sea zone dispute between Vietnam and China is heating up. Or that geopolitical hotspots in Libya and Thailand are in play.

That explains the big drop in precious metals today. Gold, as represented by the Gold Trust SPDR (GLD), dropped 2.1 percent to levels not seen since February. Also, exchange-traded funds connected to Wall Street's "fear gauge" -- the CBOE Volatility Index, the VIX -- have also been in free fall all month.

However, about those blemishes.

Breadth has been lackluster (up volume accounted for only 68 percent of total NYSE volume Friday, down from 84 percent from the week before and nearly 90 percent at the beginning of March). And the percentage of S&P 500 stocks above their 50-day moving averages -- indicating how much support the index is enjoying from its component stocks as it soars to new heights -- stood at just 60 percent on Friday, down from a high of nearly 85 percent in early April.

And finally, the ferocity of the collapse in the fear gauge could be a possible indicator of complacency among investors. The VIX inched up slightly on Tuesday, after dropping on Friday to levels that have been seen only once before (briefly in early 2013) since the market topped in 2007.

As a result, the VIX has been stuck under the 15 level for more than a month and is well below its 50-day and 200-day moving averages. According to Jason Goepfert at SentimenTrader, the last 30 years of market history suggests, with a high probability, that a 20 percent increase in the VIX is to be expected in the coming months.

There have been 15 other occurrences like the current one, and each time at some point over the next month, the VIX jumped more than 13%. And it wound up bouncing up more than 20 percent every time, with a median gain of +45 percent at its highest point.

Based on this history, it means there's a 100 percent probability that the VIX will close above 14.4 at some point by late August, with a move back above 17.4 likely. And as the VIX increases, and fear along with it, stocks will fall.

But for now, with investors excited by the turnaround in biotech and a calming of the tension between Ukraine and Russia, things are looking up.