In a letter to Henry Jones (1868), Mill clarifies (or attempts to
clarify) the infamous passage in the proof concerning the shift from
the individual to the aggregate.
Mill writes: "As to the sentence you quote from my “Utilitarianism”;
when I said that the general happiness is a good to the aggregate of
all persons I did not mean that every human being’s happiness is a
good to every other human being; though I think, in a good state of
society & education it would be so. I merely meant in this particular
sentence to argue that since A’s happiness is a good, B’s a good, C’s
a good, &c., the sum of all these goods must be a good."
(The sentence Jones quoted from *Utilitarianism*: “No reason can be
given why the general happiness is desirable except that each
person . . . desires his own happiness. This, however, being a fact,
we have . . . all the proof which the case admits of . . . that each
person’s happiness is a good to that person, and the general
happiness, therefore, a good to the aggregate of all persons.”)
This letter to Jones is in CW XVI:
http://oll.libertyfund.org/index.php?option=com_staticxt&staticfile=show.php%3Ftitle=253&layout=html
It is letter # 1257.
Anyhow, I found this quote interesting. It could suggest what might
and might not be included in a charitable reconstruction of his
proof.
Theron