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notices a surprising phenomenon. Now if he
has a high admiration of Mill's Logic, as
many chemists have, he will remember
that Mill tells him that he must work
on the principle that, under precisely the
same circumstances like phenomena are
produced. Why does he then not note
that this phenomenon was produced
on such a day of the week, the planets
presenting a certain configuration,
his daughter having on a blue dress, he
having dreamed of a white horse the night
before, the milkman having been late
that morning, and so on? The answer will
be that in early days chemists did use