Er.. the term "sound currency"/"sound money" is used to describe currencies with tangible value, e.g. backed by gold. Gold itself is considered "sound money."

Er.. the term "sound currency"/"sound money" is used to describe currencies with tangible value, e.g. backed by gold. Gold itself is considered "sound money." What you're saying about sound money and/or deflationary (what I think you intend to say is disinflationary) is highly contested. The modern U.S. Dollar is represented by Federal Reserve Notes, which are simply nominal liabilities of the central bank. Before dollars were Federal Reserve Notes, they were Silver Certificates, redeemable as silver from the U.S. government. The Federal Reserve Note is a very young experiment, far from proven, and to make an argument from authority that of course Janet Yellen knows that FRNs and modern monetary theory is correct and proven is just plain wrong.