Agassi has attacked subjectivism, for example, in his paper "Subjectivism — from infantile disease to chronic illness," and at first this made me wonder why I had been invited to contribute to the Festschrift. For much of my work in the philosophy of science and in statistics has a sub–jectivistic slant. To some extent I agree with him because, for example, I believe that the aim of a subjectivistic theory is to reduce subjectivism. But I believe it is impossible to cure the "disease" entirely, and that is where Agassi and I part company. I regard my basic position as so obvious as not to be worth defending directly and I thought it would be more useful to defend it indirectly by reviewing my work on the mathematics of the philosophy of science. It has a coherence that would be difficult to explain if my basic position was without merit.