bothering--for the present, at any rate--about actually bringing it to
account in any way?

The use to which his ideas had to be put gave Dr. Reed an excellent
test of their reliability. No doubt he passed through many stages of
doubt as he investigated one theory after another. And he could not
feel reasonably sure that he was right and had mastered his problem
until his final hypothesis had been shown to hold good under varying
actual conditions.

What test has the ordinary student for knowing when he knows a thing
well enough to leave it? He may set up specific purposes to be
accomplished, as has been suggested. Yet even these may be only ideas;
what means has he for knowing when they have been attained? It is a
long distance from the first approach to an important thought, to its
final assimilation, and nothing is easier than to stop too soon. If
there are any waymarks along the road, indicating the different stages
reached; particularly, if there is a recognizable endpoint assuring
mastery, one might avoid many dangerous headers by knowing the fact.
Or is that particularly what recitations and marks are for? And
instead of expecting an independent way of determining when he has
mastered a subject, should the student simply rely upon his teacher to
acquaint him with that fact?

_7. The tentative attitude as a seventh factor in study_

Investigators of the source of yellow fever previous to Dr. Reed
reached conclusions as well as he. But, in the light of later
discovery, they appear hasty and foolish, to the extent that they were
insisted upon as correct. A large percentage of the so-called