As the market has risen in three of the last four weeks, option traders have continued to increase their interest in trading bullish calls.

The 21-day moving average on the CBOE Equity Put/Call Ratio dropped to 0.5667 last Thursday, the lowest reading since March 2011.

Granted this is only one sentiment indicator, but it is the extremely low level (extreme optimism) that catches the eye.

The Investors Intelligence ratio has been on the rise over the last four weeks. The ratio hit a low of 1.56 back on Sept. 4, but has since jumped to 2.15 in the latest report.

The other sentiment indicator I watch closely is the CBOE Volatility Index (VIX). The VIX had fallen sharply (increasing optimism) from the beginning of September until this past week, but it has since jumped sharply.

After dropping as low as 12.52 on Sept. 20, the VIX spiked higher during last week's market decline.

With the impending government shutdown, at least it is impending as I write this, the market has shown a little more fear, and as a result the VIX spiked as high as 17.49 on Monday.

The market is vulnerable right now and the showdown in Washington might just be the catalyst that sends the market lower over the next few weeks.