igns of disease and the
treatment that was appropriate. All were beautifully interdigitated in a
logical fashion, and for any recommended therapy a good reason could be
found. There was, however, a serious difficulty. If anyone were so bold
as to ask, _But how do you know?_ only a rather lame answer would come
forth. The exposition rested in large part on authority or else largely
on reasoning from accepted premises--a "just" reasoning. And while much
keen observation was duly recorded and a considerable mass of fact
underlay the theoretical superstructure, the idea of empirical proof was
not current. Riverius chopped logic vigorously and drew conclusions from
unsupported assertions in a way that strikes us as reckless.

For a body of knowledge to be a science, it must indicate a logical
connection between first principles, which were "universal," and the
particular case. The well-educated physician could always give a logical
reason for what he did. The empiric, however, was one who carried out
his remedies or procedures without being able to tell _why_. That is, he
could not trace out the logical connection between first principles and
the particular case.

Galenism suffered especially from logical systematization, and the
system of van Helmont, while far less orderly, also had its own basic
principles on which all else depended. Boyle, however, practiced
medicine on a thoroughly different basis. He did not depend on system or
logic. In the words that Hunter used to Jenner over a hundred years
later, other physicians would _think_ the answers to their problems.
Boyle, however, preferred to _try the experiment_. He wanted _facts_.

But this attitude, which sounds so modern, so praiseworthy and
enlightened, had one serious flaw. What _was_ a fact? And how did you
know? This important problem, so significant for the growth of
scientific medicine, we can study quite readily in the works of Robert
Boyle.

The problem, in a sense, resolves around the notion of credulity. What
shall we believe? Boyle makes some distinctions between what he has seen
with his own eyes and what other people report to have seen. Thus, he
mentions "a very experienced and sober gentleman, who is much talked of"
who cured cancer of the female breast "by the outward application of an
indolent powder, some of which he also gave me." But, he adds
cautiously, he has not yet "had the opportunity to make trial of
it."[52] Clearly, since he cannot mak