The broadest definition of liberty is indeterminism with respect to a certain action. Its opposite is necessity which signifies a single determined course. There are a number of different types of necessity.
- Physical necessity: All material beings (living and non-living) are subject to external agents (which themselves are normally physical). Thus rocks and rooks are subject to the influence of gravity and the wind. This type of necessity includes the laws of physics and chemistry.
- Biological necessity: All living beings are subject to internal principles. The instincts of animals and the phototropism of plants (or plants' ability to move towards light) are examples of internal principles in living beings. Other internal principles include such activities as nutrition, elimination, reproduction, and growth. These are necessities in that they do not vary over time, but are species specific. All rational beings are exempt from biological necessity and thus have liberty of choice.
- Moral necessity: All rational beings while exempt from biological necessity and possessing the ability to resist mechanical forces (which other living beings share) are determined to one course because they depend on the will of another. The superior will on which the inferior will depends is called authority. The superior will exerts its influence by means of rewards and penalties. Morally all inferior rational beings are bound to obey a superior will, but because they have liberty of choice they are capable of disobeying.
- Logical necessity: Every rational being's thoughts are subject to the laws of logic. Logical necessity is the property, which certain logical arguments have, in which it is impossible for the conclusion to be false given that the premise(s) are true.
- Metaphysical necessity: Closely related and prior to logical necessity is metaphysical necessity. Metaphysical necessity guarantees that all beings act in accordance with their natures. Thus an ant will never act like a dog. A human will never grow wings and fly. Any being which is good by nature can do no evil. Metaphysical necessity is that which determines that the goal which every human being by nature seeks is happiness.
As
far as human liberty is concerned a masterful (and I believe
definitive) analysis of liberty was accomplished by the philosopher
Mortimer Adler in his The Idea of Freedom: A Dialectical Examination of the Conceptions of Freedom.
In this book Dr. Adler examines the history of the idea of freedom as
seen in the writings of practically all of the major Western
philosophers. He comes to the conclusion that there are three main
distinct conceptions of freedom that these philosophers have used:
- Circumstantial freedom of self-realization: This is the freedom that people think about when they think about doing what you want. Due to internal and external factors it is not always possible to do what you want. An example of limiting circumstances would be a prison for a prisoner.
- Natural freedom of self-determination: This is the freedom which corresponds to free will. It is natural because the will is naturally free and cannot be coerced into doing anything wrong without its consent.
- Acquired freedom of self-perfection: This is the freedom which corresponds to holiness. For those who have taken the necessary steps, they have gained the freedom which consists of consistently doing good.
