Thomas Aquinas's use of the terms libero, libertas, and liberum arbitrium in the Summa theologiae gives us a wealth of information about free will and freedom. Human beings have free will and are masters of themselves through their free will. Free will can be impeded by obstacles or ignorance but naturally moves toward God. According to Servais Pinckaers, our freedom can be that of indifference (the morality of obligation) or that of excellence (the morality of happiness). The difference is that of free will moving reason versus reason moving free will. The freedom of indifference is the power to choose between good and evil. The will is inclined toward neither and freely chooses between them. The freedom for excellence is the power to be the best human being we can be. Here the rules, or what makes for a good human being, are the grounding for freedom. One who observes these rules has the freedom to become excellent. According to Aquinas, intellect and will have command over free will. This then is true freedom, and on this Aquinas and Pinckaers agree. We do not have freedom of indifference, we have freedom for excellence. Anything else makes us slaves.