Austrians do rely on empirical evidence. Any proposition in the Austrian system must be based on empirical observation.
It's just that they reject the idea that economics is an empirical science. It's a logical science.
If you want further explanation, ask a question and I'll answer it.
Austrians differ from monetarists in a couple of important respects.
The Austrian school recognise that money is a market phenomenon. It always originates in markets, and never with governments. The reason is because
a) there's no example in the history of the world of money having originated from governments. Government fiat money always piggy-backs on - and ultimately hijacks - a pre-existing market-originated money.
b) if government originated a money, it would need so specify the structure of production - the price of everything in relation to the price of everything else - on day one. Needless to say, no government has had, or could ever have the knowledge to do that.
Austrians see no role for the government in managing the money supply, other than to enforce the law against fraud and breach of contract. The reason is, because it's not necessary or desirable for the government to manage it. It's not necessary because money is a market phenomenon. It's not desirable because granting a monopoly of printing money - to anyone - is just a licence to commit fraud and corruption on a massive scale, which we are now witnessing in the USA and the EU because of government "management" of the money supply.
The monetarists are generally sympathetic to free market arguments. But money, they say, is different. They believe that the money supply needs to be increased in proportion to the increase in population or increase in GDP.
(The Austrian says that since money is the *medium* of exchange, therefore it's the *relative* amount of money that's important, not the absolute amount. For example if gold were money, and the GDP increased, the demand for money increased, all it means is that you'd use a smaller piece of gold to do the same transaction. And if there wasn't enough gold, so that the "price" of something was a microscopic amount, you'd just use silver instead, or copper or whatever - just like people did before government imposed its monopoly of paper rubbish.)
So the monetarists say that the money supply needs to be steadily increased, but not too much. To do that, they say, it must be protected from political influence because the politicians can't be trusted. Therefore they say, you need an independent central bank to constantly inflate the money supply. And the justification of that bank is precisely that it is *not* answerable to elected representatives(!).
The Austrians say that constant inflation is what causes the whole cycle of boom and bust. It's what causes bubbles, because the newly printed money enters the economy at some point, and that's what causes bubbles. And the boom must eventually collapse.
Austrians deny that government can ever have the knowledge, the capacity, or the disinterestedness to manage the money supply, and say we would have been much better off if they had never meddled with it. Less wars, less tax, less depressions, less cronyism, less bureaucracy, more freedom, more peace, more abundance.
It's probably the biggest difference between the Austrians and the monetarists.
By the way, the empirical evidence makes a perfect fit with Austrian theory; and completely disproves monetarist theory. The wise hand of the Fed was constantly inflating the money supply leading into and during the crisis, and now? What explanation can they possibly have that is not circular?
"Human Action" by Ludwig von Mises
"Free to Choose" by Milton Friedman