There may be exceptional cases where vice is innate, as is idiocy or insanity, but the records of prisons and reformatories where a moral influence has been attempted, show us that germs of good may exist even in those apparently wholly given over to vice. It is true that the capacity for moral education is narrowed with every added year of life; but it is impossible for us to say, with certainty, how great this decrease of capacity may be.[79] The most essential influence for moral betterment is that which the personality of an earnest human being exerts by example and precept. The awakening and strengthening of good impulses is not, however, the immediate destruction of the bad; and struggle is often necessary if the good shall conquer. The more frequent the victory, the easier it becomes. Every virtue can be acquired at least in some degree, if the wish to acquire it be sufficiently strong and persistent. But although such struggle as this is often necessary, exactly the sign of the attainment of virtue consists in the absence of self-compulsion; by this absence, its perfection is measured. The assertion, occasionally heard, that virtue is in proportion to struggle, amounts to the contradictory assertion that the more perfect the man is, the less is his virtue. The truths which, imperfectly comprehended, lead to this opinion, are these: We distinguish by the name of virtue that moral constitution which rises above the average. It is presupposed, however, that its possessor has, in general, the impulses and capacities belonging to human nature; he could not be called temperate in any particular direction, if he did not possess the capacity of enjoyment which leads many to intemperance. Moreover, the control of strong impulses from a desire to do right presupposes a strong sense of duty; and it is on account of this sense of duty that we respect a man. But if an individual distinguished by a strong sense of duty gradually succeeds in tempering his impulses and ridding himself of his faults, his virtue is not less, but more perfect. And finally, the fact is also to be taken into consideration that, while one cannot necessarily conclude, from a man's innate love for some especial class of good actions, that he will do his duty in other directions also, this is an inference which can be drawn where actions are performed from a sense of duty. A certain degree of intelligence is a condition of virtue; a being without reason is not a moral being, as the animal is not; but morality requires only average human intelligence. There is no greater error than the opinion that virtue is not concerned with action; for virtue is excellence of character which leads to right action; action is the test of moral worth. In olden times, an attempt was often made to set up one especial form of character as universal ideal. Such an attempt is injustifiable, since the nature and circumstances of individuals differ. In morality, too, there may be originality.