On Wednesday the Federal Reserve shared its thoughts on the course of interest rates—but not on the implications for the value of the dollar. The two can't be disconnected. The Fed's rationale on interest rates determines the stability of the dollar, which is the economic bedrock for price stability, capital inflows, growth and jobs.

Obfuscation on the dollar works fine for Wall Street, which reaps billions in profits from the Fed's unstable dollar policy. It trades currencies and volatility, and makes a bundle protecting...