Just like the financial market, taxation, the domain of public finances, is torn between two trends: one with a dynamic future, and so progressive and the other static, frozen in time, resistant to change, and so conservative.
The two bullish or bearish visions are on opposite sides of the fence, but beyond this similarity with financial markets, they are two more general visions which are confronting each other and which assess the problems to be overcome in two different ways.
I like Winston Churchill's quote on pessimism and optimism: "A pessimist see a problem in every opportunity and the optimist sees an opportunity in every problem."