How often have you heard it? Monetary policy is impotent because interest rates are very low and if you increase the money base banks will just hoard all the money and will not lend out anything. Market Monetarists of course know that this is nonsense, but we have all also tried to explain this to people that seem unable to listen to the arguments.
Here is an idea how you make people listen. If somebody refuses to accept the power of monetary policy just ask them the following question: “So if an increase in the money base will not be able to increase nominal GDP why should we then have taxes?”
Hence, if there indeed were a liquidity trap there would indeed be a free lunch – you could pay for all expenditure with newly printed money from the central bank without getting inflation. This statement will normally upset people quite a bit and they will scream at you “then we will get hyperinflation!”…when you hear that you know you won the argument and you just reply “Q.E.D.”.
PS I am not suggesting this – exactly because I know there is no liquidity trap.