Mill’s conversion: The herschel connection

Between the first and second editions of A System of Logic, John Stuart Mill underwent a startling conversion from an uncompromising frequentist philosophy of probability to a thoroughly Bayesian degree-of-belief view. The conversion was effected by correspondence with the eminent scientist Sir John Herschel, to whom Mill already owed what have become known as Mill's Methods of Experimental Inference. We present the relevant correspondence, and discuss the extent of Mill's conversion