The amount of money in a nation's money supply is crucial to the health of its economy. If there is not enough money in circulation, the economy cannot grow.
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That's just a part of Econ101. It's one of many basic economic principles that very few people here seem to understand.
This is not true, regardless of whether you're a Keynesian or an Austrian economist. The quantity theory of money states that
M V = P Q, (1)
where M = money supply, V = money velocity, P = price level, Q = real output (goods, service, etc). I think the vast majority of economists agree with this equation, although their opinion may differ on how it should be used.
It is common to associate a growing economy with growing real output, Q (i.e., more goods being produced, more services being used, etc.). If you re-arrange Eq. (1) to solve for real output, Q, you get
Q = M V / P .
So real output, Q, can grow three different ways (or more properly, it has 3 degrees of freedom):
1. Money supply, M, can increase (what you said).
2. Money velocity, V, can increase (e.g., an increase in the rate that bitcoin-days are destroyed)
3. Price level, P, can
decrease (the feared deflationary spiral).