ABSTRACT
"The problem of the criterion" seems to the author to be one of the most important and one of the most difficult of all the problems of philosophy. The mind cannot attain to certainty until it has found within itself a sufficient reason for adhering to the testimony of such an authority. The criterion should be objective. The ultimate reason for believing cannot be a merely subjective state of the thinking subject. A man is aware that he can reflect upon his psychological states in order to control them. Knowing that he has this ability, he does not, so long as he has not made use of it, have the right to be sure. David Hume followed Locke in this empiricism and said that empiricism gives people an effective criterion for distinguishing the good apples from the bad ones. The great Scottish philosopher Thomas Reid reflected on all this in the eighteenth century.
