fact that a brazier of burning charcoal was at the same time in the
apartment with no sufficient outlet for its fumes. Prince Eugene
is said to have received a poisoned letter, which he suspected and
immediately threw from him. To ascertain whether his suspicions were
well founded the letter was administered to a dog, which, to make
assurance doubly sure, was fortified by an antidote. The dog died, but
no inquiry seems to have been made into the character of the antidote.

Hotspur's retort to Glendower showed a sound sense of the true value
to be attached to mere priority.

_Glendower_. At my nativity
The front of heaven was full of fiery shapes,
Of burning cressets: and at my birth
The frame and huge foundation of the earth
Shaked like a coward.

_Hotspur_. Why so it would have done at the same season, if
your mother's cat had but kittened, though yourself had never
been born.

1 Hen. IV., 3, 1, 13.

We all admit at once that the retort was just. What principle of sound
conclusion was involved in it? It is the business of Inductive Logic
to make such principles explicit.

Taking _Post Hoc ergo Propter Hoc_ as a generic name for fallacious
arguments of causation based on observed facts, for the fallacious
proof of causation from experience, the question for Logic is, What
more than mere _sequence_ is required to prove _consequence?_ When do
observations of _Post Hoc_ warrant the conclusion _Propter Hoc?_

II.--MEANING OF "CAUSE".--METHODS OF OBSERVATION--MILL'S EXPERIMENTAL
METHODS.

The methods formulated by Mill under the name of Experimental Methods
are methods actually practised by men of science with satisfactory
results, and are perfectly sound in principle. They were, indeed, in
substance, taken by him from the practice of the scientific laboratory
and study as generalised by Herschel. In effect what Mill did was to
restate them and fit them into a system. But the controversies into
which he was tempted in so doing have somewhat obscured their exact
function in scientific inquiry. Hostile critics, finding that they did
not serve the ends that he seemed to claim for them, have jumped to
the conclusion that they are altogether illusory and serve no purpose
at all.

First, we must dismiss the notion, encouraged by Mill's general theory
of Inference, that the Experimental Methods have anything special to
do with the observation and infe