Economics was time ago dubbed as the ‘sad science,’ because of its intrinsic predictive limitations, in spite of its colossal mathematical foundation. In this regard, economic libraries seem to disprove Galileo’s abused saying that ‘the book of nature is written in mathematical language.’ It might be so only because we, humans, so decided.[1] Alas, portions of this book do not seem to respond very well to mathematics.[2] Marxists and neo-Keynesians differently embraced the need to change economics in a ‘happy’ science, finally able, as all the rest of the successful sciences, to predict future facts and events through mathematical calculations over axioms and logical derivations. They tried the endeavor differently.