Another precaution for the critic who would retain clearness of vision is the avoidance of abstract systems, which petrify and hinder the necessary flexibility of mind. Coolness of temper is also enjoined and scrupulously practiced. "It is only by remaining collected ... that the critic can do the practical man any service"; and again: "Even in one's ridicule one must preserve a sweetness and good humor" (letter to his mother, October 27, 1863). In addition to these virtues, which in Arnold's opinion comprised the qualities most requisite for salutary criticism, certain others are strikingly illustrated by Arnold's own mind and methods: the endeavor to understand, to sympathize with, and to guide intelligently the main tendencies of his age, rather than violently to oppose them; at the same time the courage to present unpleasant antidotes to its faults and to keep from fostering a people in its own conceit; and finally, amidst many discouragements, the retention of a high faith in spiritual progress and an unwavering belief that the ideal life is "the normal life as we shall one day see it." Criticism, to be effective, requires also an adequate style. In Arnold's discussion of style, much stress is laid on its basis in character, and much upon the transparent quality of true style which allows that basic character to shine through. Such words as "limpidness," "simplicity," "lucidity," are favorites. Clearness and effectiveness are the qualities that he most highly valued. The latter he gained especially through the crystallization of his thought into certain telling phrases, such as "Philistinism," "sweetness and light," "the grand style," etc. That this habit was attended with dangers, that his readers were likely to get hold of his phrases and think that they had thereby mastered his thought, he realized. Perhaps he hardly realized the danger to the coiner of apothegms himself, that of being content with a half truth when the whole truth cannot be conveniently crowded into narrow compass. Herein lies, I think, the chief source of Arnold's occasional failure to quite satisfy our sense of adequacy or of justice, as, for instance, in his celebrated handling of the four ways of regarding nature, or the passage in which he describes the sterner self of the working-class as liking "bawling, hustling, and smashing; the lighter self, beer."