My opinion is that inflation does not drive economic growth.
> Are they right and both deflation and inflation can supply economic growth?
Neither one supplies economic growth.
> does that mean another factor is the main proponent for growth?
Increased productive capacity is the source of economic growth. Not the supply of currency.
Take a simple example.
Three people live on an island after a plane crash.
They fish, build huts, make tools. To facilitate exchange, they use paper money from the game Monopoly happened to survive among the wreckage.
One day a new box of Monopoly washes ashore, including a fresh supply of Monopoly money.
Their money supply has doubled.
Will they experience any economic growth? Clearly not.
The next day a power saw and generator wash ashore. They have new tools and increased productive capacity.
Will they experience any economic growth? Clearly they will.