I have a terribly misinformed question:
Why can't deflation be combated by printing more money? Can inflation be used in this manner?
Printing money can be used to counteract deflation. It was used in Japan, after they dropped interest rates to 0. However, it didn't really solve the problem, as deflation remained for over a decade (it's been argued that the BoJ didn't print enough).
It's been used in the UK when the Bank of England printed £200 billion in 2008-2009, after the economy continued to crumble despite interest rates being cut to virtually 0. This amount of printing was unprecedented (and when corrected for the size of the economy, this was something like 5x the amount that Japan printed).
The Federal Reserve bank has also been printing $, but on a smaller level.
The problem with printing, is what you actually do with the money. In all these 3 cases, the money was used to buy government bonds. These are mainly owned by commercial banks (as an ultra-safe investment, and an alternative to stocks or other more risky investments). The idea is that if the central bank can buy all the ultra-safe investments up with printed cash, banks and other investors will have no choice but to spend the cash on making risky investments (e.g. loans to small businesses, mortgage lending, business ventures, etc.)
In fact, what we saw in the UK, was that quite a lot of this newly printed money *didn't* get invested into risky investments. The investors (mainly commercial banks) just hoarded the cash, and accepted that they were getting 0 interest for it as the price of having guaranteed safety (but hey, making 0% isn't too bad when interest rates are almost zero).
This is the same problem that you get with just lowering interest rates to 0. It's known as a 'liquidity trap' - once investors are scared off from risk, it's very difficult to entice them back. And unless you get investors wanting to buy stocks, houses, commercial real estate, or invest in new businesses (that would need new buildings, computers, trucks, etc.) then you end up with reduced demand, falling prices and deflation.
There is also risk with printing money, that it could stimulate inflation. One of the problems when a liquidity trap occurs, is that huge pools of idle cash build up in the economy - and if conditions turn, then you can get a very quick, and overheated recovery - causing a spike of, potentially very severe, inflation. This is theoretical, and we haven't seen it happen in any country that has used printing in a controlled way.