Good habits of the mind, enabling it to be a more efficient instrument of knowledge. They are distinguished from the moral virtues, since they do not, as such, make one a better person. They make one more effective in the use of what he or she knows and, to that extent, contribute to the practice of moral virtue. According to Aristotle and St. Thomas Aquinas, there are five intellectual virtues: three pertaining to the theoretical or speculative intellect concerned with the contemplation of the true; and two pertaining to the practical intellect, concerned with the two forms of action, making and doing.
The three speculative intellectual virtues are understanding, science, and wisdom. Understanding (Greek nous, intuitive mind) is the habit of first principles. It is the habitual knowledge of primary self-evident truths that lie at the root of all knowledge. Science (Greek epist_m_, knowledge) is the habit of conclusions drawn by demonstration from first principles. It is the habitual knowledge of the particular sciences. Wisdom (Greek sophia, wisdom) is the habit of knowing things in their highest causes. It is the organized knowledge of all principles and conclusions in the truth called philosophy.
The two practical intellectual virtues are art and prudence. Art (Greek techne, craftsmanship) is the habit of knowing how to make things, how to produce some external object. As a practical virtue, it includes the mechanical and fine arts and most liberal arts. Prudence (Greek phron_sis, practical wisdom) is the habit of knowing how to do things, how to direct activity that does not result in tangible products. It enables one to live a good human life and is the only one of the intellectual virtues that cannot exist apart from the moral virtues.