therefore, that on this subject, at least, Galen was not
infallible; and it would naturally follow that, one fallible
point having been revealed, others would be sought for. In other
words, scepticism in regard to accepted methods would be aroused,
and would lead naturally, as such scepticism usually does, to
progress. The devastating effects of these plagues, despite
prayers and incantations, would arouse doubt in the minds of many
as to the efficacy of superstitious rites and ceremonies in
curing diseases. They had seen thousands and tens of thousands of
their fellow-beings swept away by these awful scourges. They had
seen the ravages of these epidemics continue for months or even
years, notwithstanding the fact that multitudes of God-fearing
people prayed hourly that such ravages might be checked. And they
must have observed also that when even very simple rules of
cleanliness and hygiene were followed there was a diminution in
the ravages of the plague, even without the aid of incantations.
Such observations as these would have a tendency to awaken a
suspicion in the minds of many of the physicians that disease was
not a manifestation of the supernatural, but a natural
phenomenon, to be treated by natural methods.

But, be the causes what they may, it is a fact that the
thirteenth century marks a turning-point, or the beginning of an
attitude of mind which resulted in bringing medicine to a much
more rational position. Among the thirteenth-century physicians,
two men are deserving of special mention. These are Arnald of
Villanova (1235-1312) and Peter of Abano (1250-1315). Both these
men suffered persecution for expressing their belief in natural,
as against the supernatural, causes of disease, and at one time
Arnald was obliged to flee from Barcelona for declaring that the