A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I
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 a dark spot with the given property, 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 that particular kind of dark spot; 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.