A System of Logic, Ratiocinative and Inductive (Vol. 1 of 2)
John Stuart Mill · en
When, however, we thus add syllogism to syllogism, we are really adding
induction to induction. Two separate inductions must have taken place to
render this chain of inference possible; inductions founded, probably, on
different sets of individual instances, but which converge in their
results, so that the instance which is the subject of inquiry comes within
the range of them both. The record of these inductions is contained in the
majors of the two syllogisms. First, we, or others for us, have examined
various objects which yielded under the given circumstances the given
precipitate, and found that they possessed the properties connoted by the
word arsenic; they were metallic, volatile, their vapour had a smell of
garlic, and so forth. Next, we, or others for us, have examined various
specimens which possessed this metallic and volatile character, whose
vapour had this smell, &c., and have invariably found that they were
poisonous. The first observation we judge that we may extend to all
substances whatever which yield the precipitate: the second, to all
metallic and volatile substances resembling those we examined; and
consequently, not to those only which are seen to be such, but to those
which are concluded to be such by the prior induction. The substance
before us is only seen to come within one of these inductions; but by
means of this one, it is brought within the other. We are still, as
before, concluding from particulars to particulars; but we are now
concluding from particulars observed, to other particulars which are not,
as in the simple case, _seen_ to resemble them in the material points, but
_inferred_ to do so, because resembling them in something else, which we
have been led by quite a different set of instances to consider as a mark
of the former resemblance.