 The entry for On Liberty in Mill’s bibliography, though, makes no mention of Taylor Mill (MacMinn et al. 1945, 92). Since he used the term “joint product” in the bibliography for the Principles, it is somewhat curious that he does not use it there for On Liberty as well. Mill’s letters to Taylor Mill and others also speak equivocally to the question of On Liberty’s production. In January of 1855, Mill writes to Taylor Mill from Rome that he has decided that a volume on liberty would be “the best thing to write &amp; publish at present” (J. S. Mill, [TLL], 294). He asks her to look at an essay on the subject that he had written in the preceding year to see if it could serve as the basis for one part of this volume, and says that if her answer is yes and if his health allows “I will try to write &amp; publish it in 1856.” In this letter, he clearly suggests that he will be the one doing the writing. (On Liberty in fact appeared in 1859.) In a reference to this projected volume in a letter of the next month, though, he says that “We must cram into it as much as possible of what we wish not to leave unsaid” (J. S. Mill, [TLL], 332). In letters to others, he refers to the essay as his and to himself as the one writing it (J. S. Mill, [TLL], 539, 581).