Government, Currency, Spending, and Taxes

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A gem of brevity:

The purpose of government [...] is to perform functions that are best handled collectively. A national currency is the central tool for doing this. It enables government to move some resources to the public sector. 

The government achieves this through spending. When the government spends its currency into existence by purchasing goods and services from non-government, these goods and services are shifted to the public sector and non-government obtains currency with which it can pay taxes.