ntended to deny. The
way of reaching certainty that Roger Bacon repudiated was argument,
discussion, dialectic. This "concludes a question but does not make us
feel certain, or acquiesce in the contemplation of truth that is not
also found in Experience". Argument is not necessarily useless; the
proposition combated is only that by it alone--by discussion that does
not go beyond accepted theories or conceptions--rational belief about
the unknown cannot be reached. The proposition affirmed is that to
this end the conclusions of argument must be tested by experience.

Observation of facts then is a cardinal part of the method of Science.
The facts on which our inferences are based, by which our conclusions
are tested, must be accurate. But in thus laying emphasis on the
necessity of accurate observation, we must beware of rushing to the
opposite extreme, and supposing that observation alone is enough.
Observation, the accurate use of the senses (by which we must
understand inner as well as outer sense), is not the whole work of
Science. We may stare at facts every minute of our waking day without
being a whit the wiser unless we exert our intellects to build upon
them or under them. To make our examination fruitful, we must have
conceptions, theories, speculations, to bring to the test. The
comparison of these with the facts is the inductive verification of
them. Science has to exercise its ingenuity both in making hypotheses
and in contriving occasions for testing them by observation. These
contrived occasions are its artificial experiments, which have come to
be called experiments simply by contrast with conclusive observations
for which Nature herself furnishes the occasion. The observations of
Science are not passive observations. The word experiment simply means
trial, and every experiment, natural or artificial, is the trial of
a hypothesis. In the language of Leonardo da Vinci, "Theory is the
general, Experiments are the soldiers".

Observation and Inference go hand in hand in the work of Science, but
with a view to a methodical exposition of its methods, we may divide
them broadly into Methods of Observation and Methods of Inference.
There are errors specially incident to Observation, and errors
specially incident to Inference. How to observe correctly and how to
make correct inferences from our observations are the two objects of
our study in Inductive Logic: we study the examples of Science because
they have b