How can one define a scholar?
The first and most important criterion is that he be capable of studying and understanding the Torah, a condition that calls for the highest possible degree of intellectual ability.
This, however, is only one facet of the fundamental outlook of the scholar.
It is not enough for him to be erudite and perceptive.
He must also be a noble human being endowed with spiritual and humanitarian qualities.
One whose deeds are not compatible with his theories–either because his morals are not beyond reproach or because he does not strictly observe the precepts–cannot be regarded as a true scholar and is therefore worse than an ignoramus.
The sages themselves said:
"The deliberate errors of the unlearned are regarded as unintentional, while the unintentional mistakes of the scholars are regarded as deliberate."
It is not enough for a scholar to preach.
He must also practice what he preaches, and when there is incongruence between theory and practice, a man can no longer be considered a scholar.
Furthermore, a learned man is expected to live in the light of his knowledge, so that everything he does or says will itself constitute Torah.
It was said of the scholar who transgressed:
"His Torah was but lip service," since true Torah must be reflected in personal behavior as in study.
These were not merely abstract moral rules but very practical halakhic precepts.
The codifiers also regarded them as such and determined that a man, however erudite, whose conduct was contemptible,could not be respected for his learning but should be condemned and despised.
It is often related in the Talmud that learned people of dubious character were punished, chastised, or excommunicated.
Thus scholarship is not merely an intellectual standard but encompasses the entire personality, the man becoming the symbol of Torah, his whole essence synonymous with it.
We can therefore understand the eagerness to study the deeds and conversations of scholars and to learn from them, given the assumption that anything done or said by the scholar can serve as a guide to others.
–Rabbi Adin Steinsaltz
From The Essential Talmud, p.260 by Rabbi Adin Steinsaltz