Jimmy Song is a bitcoin advocate, developer and author who has been contributing to open-source bitcoin projects since 2013.

Previously working as a software developer in a number of industries, Song joined Monetas, a crypto-finance software company, in 2014. After a one-year stint, Song joined Armory Technologies, an open-source bitcoin wallet management platform, to develop a bitcoin wallet intended for enterprise business. He then became the principal architect for Paxos, a New York-based financial institution and stablecoin issuer.

In January 2018 Song joined Blockchain Capital, a company focused on funding projects based on blockchain technology, as a bitcoin fellow. In 2019 he published “Programming Bitcoin,” a book that aims to teach readers the basics of bitcoin. In addition to his book, he runs a for-profit company, Programming Blockchain, that instructs students around the globe on different techniques to develop bitcoin.

In January 2019, Song began lecturing as a professor of two graduate-level courses at the University of Texas at Austin. He also began serving as an expert witness in certain events involving bitcoin.

Song is well known for arguing that blockchains have limited use cases. More specifically, he has argued that the blockchain’s sole use case is for “sound money” – which is how he characterizes bitcoin. He has been a vocal critic of permissioned blockchains, alternative cryptocurrencies and the argument that Ethereum will decentralize the internet.

Read more: Decentralized or Nothing: Song Duels IBM Over Blockchain Hype at SXSW

Song has made several bets about the future of blockchain with Joseph Lubin, an Ethereum co-founder and the founder of ethereum venture studio ConsenSys.

At CoinDesk’s 2018 Consensus conference Lubin bet Song “any amount of bitcoin” that Ethereum’s decentralized applications would not have a significant number of users in the next five years. At CoinDesk’s Consensus 2019, Song and Lubin defined the terms of the previous wager and agreed that the winner of the bet would walk away with 810.8 ETH or 69.74 BTC depending on who wins.