Mortimer Adler's work was always encyclopedic. He is perhaps best known as the editor of the Great Books of the Western World (1952, 52 volumes), and its companion A Syntopicon: An Index to The Great Ideas (1952, 2 volumes).

But even the books written directly by Adler are encyclopedic in nature, especially his two-volume survey on freedom - The Idea of Freedom: A Dialectical Examination of the Conceptions of Freedom (1958) and its sequel The Idea of Freedom: A Dialectical Examination of the Controversies about Freedom (1961).

In The Idea of Freedom, vol.I, Adler classifies all freedoms into three categories:

• The Circumstantial Freedom of Self-Realization
• The Acquired Freedom of Self-Perfection
• The Natural Freedom of Self-Determination

Self-realization is freedom from external coercion, political end economic freedom, etc.

The freedom we have identified as circumstantial is variously called "economic freedom," "political freedom," "civil liberty," "individual freedom," "the freedom of man in society," "freedom in relation to the state," and "external freedom." It is sometimes referred to negatively as "freedom from coercion or restraint," "freedom from restrictions," or "freedom from law," and sometimes positively as "freedom of action," "freedom of spontaneity," or "freedom under law." (p.127)

Freedom from these constraints is the kind of freedom worth having stressed by the classical compatibilists from Thomas Hobbes on.

Today most philosophers might include a large number of circumstantial internal constraints on freedom such as an agent's mental disabilities, addictions, behavioral conditioning, both normal and coercive (indoctrination or brainwashing), and perhaps even factors like heredity and environment.

Self-perfection is the idea from Plato to Kant that we are only free when our decisions are for reasons and we are not slaves to our passions (making moral choices rather than satisfying desires).

This is the acquired or learned knowledge to distinguish right from wrong, good from evil, true from false, etc. Adler also includes many theologically minded philosophers who argue that man is only free when following a divine moral law. Sinners, they say, do not have free will, which is odd because sinners are presumably responsible for evil in the world despite an omniscient and omnipotent God.

As signifying one of the three ways in which writers think that men possess freedom, the word "acquired" refers to that the possession of which depends upon a change or development in human beings whereby they have a state of mind, or character, or personality which differentiates them from other men.

Whatever word is used to designate this difference (whether it be "good," "wise," "virtuous," "righteous," "holy," "healthy," "sound," "flexible," etc.), the difference represents an improvement, or the attainment of a superior condition, as measured on whatever scale of values is posited by the particular writer.

Freedom, in other words, is thought to be possessed only in conjunction with a certain state of mind, character, or personality that marks one man as somehow "better" than another. (p.135)

Self-determination covers the classic problem of free will. Are our actions "up to us," could we have done otherwise, are there alternative possibilities, or is everything simply part of a great causal chain leading to a single possible future?

Most of Adler's natural freedoms are compatibilisms. They include Hegel's freedom of a stone falling according to Newton's law of gravity.

Adler defines the natural freedom of self-determination as that which is not either circumstantial or acquired.

A freedom that is natural is one which is (i) inherent in all men, (ii) regardless of the circumstances under which they live and (iii) without regard to any state of mind or character which they may or may not acquire in the course of their lives. (p.149)

In his over 1400 pages, Adler devotes only six pages to brief comments on quantum mechanical indeterminism ⁵³ (v.1, p.461-466). Adler depends heavily on the thoughts of Max Planck and Erwin Schrödinger, who along with major thinkers like Einstein, Louis de Broglie, and David Bohm, rejected indeterminism.