The Great Divide between the Austrian and the Gossen Schools: Analyzing Hypothetical Equilibrium Prices or Analyzing Actual Market Prices

Just as the classical economists had done before them, the Gossen School analyzed prices as they would be if certain special conditions were fulfilled: they analyzed hypothetical equilibrium prices rather than actual market prices. It is here, then, that we find the great divide between the Austrian and the Gossen Schools. Menger paved the way for dealing with real-world prices. His work made economics more scientific in the true sense of the word—increasing knowledge about real things—while the writings of Gossen, Jevons, and Walras dealt not with matters of fact, but only conjectures.

--Jörg Guido Hülsmann, Mises: The Last Knight of Liberalism (Auburn, AL: Ludwig von Mises Institute, 2007), 134.