New York University economics professor and self-described “crypto-skeptic” Nouriel Roubini and Ethereum (ETH) developer Joe Lubin have a major difference of opinion on the future of cryptocurrencies.

Their debate Thursday during the Fluidity Summit in New York covered many of the topics discussed during the conference including decentralization, regulation, infrastructure and income inequality.

Roubini, once known as “Dr. Doom” for his pronouncements, argued that while central banks and fiat currency were not the cause of the 2008 financial crisis, “a significant revolution [is] needed in financial services” and that this revolution is already taking place in financial technology, or fintech, rather than the growth of cryptocurrencies.

“Fintech today, it has nothing to do with crypto-blockchain,” Roubini said. “It has to do with [artificial intelligence] and the Internet of Things. It’s revolutionizing things like insurance [and] asset management.”

Lubin defended cryptocurrencies and discussed the need to fix what he said is a broken internet, arguing that blockchain is the best solution to the challenges of the financial system. He noted that “perfect decentralization is a bit of an exaggeration,” that data mining has “turned into a hardware arms race” and that regulation is needed. It’s not that cryptocurrencies are inherently subject to fraud, he said, but that fraud has always existed on the web.