The scientist in charge of the above-mentioned investigation was, no
doubt, a modest man. Yet he saw fit to question the old assumption
that yellow fever was spread by invisible particles called "fomites."
Indeed, he had the boldness to disprove it. Then he disproved, also,
the assumption that the fever was contagious by contact. After that he
set out to test a hypothesis of his own. His attitude toward the
results of former investigations was thus skeptically critical. Every
proposition was to be questioned, and the evidence of facts, rather
than personal authority or the authority of time, was the sole final
test of validity.

What should be the attitude of the young student toward the
authorities that he studies? Certainly authors are, as a rule, more
mature and far better informed upon the subjects that they discuss
than he, otherwise he would not be pursuing them. Are they still so
prone to error that he should be critical toward them? At any rate,
should he set himself up as their judge; at times condemning some of
their statements outright, or accepting them only in part,--and thus
maintain independent views? Or would that be the height of presumption
on his part? While it is true that all authors are liable to error,
are they much less liable to it in their chosen fields than he, and
can he more safely trust them than himself? And should he, therefore,
being a learner, adopt a docile, passive attitude, and accept whatever
statements are presented? Or, finally, is neither of these attitudes
correct? Instead of either condemning or accepting authors, is it his
duty merely to understand and remember what they say?

_5. Memorizing, as a fifth factor in study_