Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

The current month of September appears to be firmly intent on challenging its historical record with regard to stocks, with yet another up day in the books -- the seventh in a row. That's right, stocks have so far risen every day this month. Today, the S&P 500 (SNPINDEX:^GSPC) added another .3%, while the narrower, price-weighted Dow Jones Industrial Average (DJINDICES:^DJI) was up 0.9%.

With that winning streak in mind, it's not surprising that the CBOE Volatility Index (VOLATILITYINDICES:^VIX) fell another 4.9% today, to close at 13.82 -- the VIX, Wall Street's "fear index," is calculated from S&P 500 option prices and reflects investor expectations for stock market volatility over the coming 30 days. The VIX has now fallen nearly 19% since the beginning of the month.

Carl Icahn's case for Apple
Yesterday, I highlighted investors' dissatisfaction with Apple's (NASDAQ:AAPL) premium pricing strategy for the lower-end model iPhone 5C it released yesterday. That process continued to play out today, with the shares declining another 5.4%, adding to yesterday's 2.3% loss.

One highly astute market participant who was unfazed by the decline is billionaire activist investor Carl Icahn, who told CNBC today:

I really think Apple is one of my best right now. At these levels, we're buying quite a bit of stock... We bought quite a bit today in the $465, $470, $467 range, $466... That's not to say it won't go any lower -- I don't really look at it from day-to-day and we don't try to fix what the market is going to do. I think if they do a big buyback, that's going to be a major plus, but I also think the products are pretty good and I think they're going to get a lot of business from China and they're going to do great anyway. You don't see companies like this with this kind of brand.

Back on August 13, Icahn tweeted that he had amassed had a large position in Apple and believed the company "to be extremely undervalued." Today, he made the case for the stock succinctly:

We look at the markets and look for no-brainers and I think Apple is just a no-brainer. It's extremely cheap -- you just look at the numbers on Apple and if you back out cash, you're really paying less than $300 billion for Apple and its EBIT [Earnings Before Interest and Taxes, a measure of cash flow] is about $50 billion, so your return is 18% or 5.6 times. But the real kicker is that if they do a huge buyback -- not even huge, $150 billion -- you're only paying three times EBIT, you're getting the 33% return. With those numbers in a company that is growing and has a great brand -- if somebody offered you that and didn't tell you the name of it, you'd pay 'em to tell you what the company was.

As far as the pricing of the new iPhone models is concerned, Icahn isn't giving it a second thought:

I will tell you, at the risk of being immodest, that we have one of the best records around over the last decade, over the last year. I will tell you this: I've learned one thing: Don't micromanage. Don't go in and tell somebody else how to run their business. I look at it from the big picture: We go into companies and we tell them how to run their finances, we tell them how to buy pencils instead of buying from their cousin Vinnie, for example. But we don't tell them what to do in this situation...

I would be the most presumptuous person in the world to sit there and tell them they shouldn't price it this way. I just look at what they're doing: They have one of the best brands, they are building revenue... I think Tim Cook is doing a very good job... Don't tell the CEO who spends 20 hours a day, hopefully, doing his job and has been doing it for thirty years, "Hey, you shouldn't go into China" or "You should..." -- that's the height of presumption.

Icahn's case for Apple may not be sufficient justification to go out and buy the stock immediately, but, given his track record, it's certainly reason enough for value hounds to prick up their ears and begin sniffing around the shares.