From the point of view of ethics, the main division of habits is into good and bad, i.e. into virtues and vices, according as they lead to actions in conformity with or against the rules of morality. It is needless to insist on the importance of habit in moral conduct; the majority of actions are performed under its influence, frequently without reflection, and in accordance with principles or prejudices to which the mind has become accustomed. The actual dictates of an upright conscience are dependent on intellectual habits, especially those of rectitude and honesty without which it happens too often that reason is used, not to find out what is right or wrong, but to justify a course of action one has taken or wishes to take. Custom also is an important factor, as that which is of frequent occurrence, even if known at first to be wrong, little by little becomes familiar, and its commission no longer produces in us feelings of shame or remorse. The voice of conscience is stifled; it ceases to give its warning, or at least no attention is paid to it.
By lessening freedom, habit also lessens the actual responsibility of the agent, for actions are less perfectly attended to, and in varying degrees escape the control of the will. But it is
important to note the distinction between habits acquired and retained knowingly, voluntarily, and with some foresight of the consequences likely to result, and habits acquired unconsciously, without our noticing them, and therefore without our thinking of the possible consequences. In the former case, actions good or bad,
though actually not quite free, are nevertheless imputable to the agent, since they are
voluntary in their cause, that is, in the implied consent given them at the beginning of the habit. If on the contrary the will had no part at all in acquiring or retaining the habit, actions proceeding from it are not voluntary, but, as soon as the existence and dangers of a bad habit are noticed, efforts to uproot it become obligatory.
CATHOLIC ENCYCLOPEDIA: Habit ]
