Pedestrians pass in front of the New York Stock Exchange. Michael Nagle | Bloomberg | Getty Images

The tax bill is almost done, so the debate is whether to sell on the news. It may be happening already. Stocks retreated on Tuesday, and even a notable rise in 10-year Treasury yields failed to move bank stocks up. (Stock prices were mixed on Wednesday.) There's reason to consider that this month's notable rally should at the very least pause.

Bears argue:

1) The market is overbought on a short-term basis. That's certainly true. The is up more than 3 percent in the last few weeks on hopes a tax cut will boost corporate profits in 2018, and banks, a sector that would greatly benefit from tax cuts, are up almost 7 percent. Markets since Nov. 27: S&P 500: up 3.2 percent

Transports: up 9.5 percent

Banks: up 6.6 percent

Russell 2000: up 2 percent

Semis: down 4.9 percent

Tech: flat Notice that technology, and particularly semiconductors, a sector that would see fewer benefits from tax cuts, has underperformed. So, to some extent, there is already a "sell on the news" mentality. 2) Stocks are expensive, even considering the tax cuts. Also true. Most analysts believe S&P 500 earnings for 2018 will increase anywhere from 8 percent to 11 percent, without tax cuts. Tax cuts, depending on whom you talk to, could add 5 percent to 7 percent to that. This puts stocks in a very expensive range: anywhere from 18.5 times to 19 times 2018 earnings without tax cuts. Throw in tax cuts, and you still have multiples of 17.5 or higher. That's closer to the historic average. Here's the problem: To really move the S&P forward on these numbers, you have to argue that the multiple should stay higher, say, close to 20. Put the multiple at 20, and with tax cuts, you can easily argue that the S&P 500 should hit 3,000 in 2018, up (an attainable) 11 percent. That's exactly what bulls are arguing. The market deserves a high multiple.

Bulls say: