The four freedoms are the core normative framework of stallman's free software philosophy — a precise, numbered definition of what it means for software to be free. They are:
The numbering starting at zero is deliberate — stallman was a programmer, and in many languages arrays are zero-indexed. Freedom 0 (to run) was added later as an explicit clarification; early formulations implied it but did not state it.
Origin and Development
The intellectual germ appears in the gnu-manifesto (1985), whose philosophical argument centers on software users' right to share and modify programs. But the four freedoms as a numbered list were not formally codified until the mid-1990s, when the free-software-foundation needed a precise definition to distinguish free software from freeware, shareware, and semi-open licenses. The free-software-definition-essay (1996 on gnu.org) is the canonical published formulation.
Stallman had been using the underlying concepts since the early 1980s — the requirement for source code access, the right to share, the right to modify — but the four-part structure gave the philosophy a teachable, enforceable shape.
Why Four, and Why These Four
The four freedoms are not a random enumeration; they address every point at which a software vendor might restrict a user. Proprietary software restricts running (through licenses that limit use cases), studying (through withholding source code), redistributing (through copyright and contract), and modifying (through the same). Each freedom addresses a specific mode of control.
stallman consistently emphasizes that all four are necessary; removing any one produces software that is not free in the relevant sense. A program that provides Freedoms 1-3 but restricts Freedom 0 — for example, software you can modify but only run for non-commercial purposes — is not free software by this definition.
The Precondition of Source Code
Freedoms 1 and 3 explicitly require access to source code. This is not incidental — it is a direct response to the practice of distributing software only in compiled binary form, which makes it effectively opaque to study and difficult to modify. The gpl-copyleft-mechanism enforces this by requiring that any distributed binary include or be accompanied by the corresponding source code.
Relationship to the Free Software Definition
The four freedoms are the substance of the free-software-definition. The definition says software is free if and only if it provides all four freedoms to all users. This makes the definition binary rather than scalar — software is either free or it is not, regardless of how many restrictions it places or how reasonable those restrictions might seem.
This all-or-nothing structure was deliberate and has been a persistent point of contention. Critics argue it is too rigid; stallman argues that any exception creates a hole through which non-freedom can enter.
Influence
The four freedoms framework was adopted and adapted by the open-source-initiative in its open-source-definition-schism, though the OSI's "open source definition" uses different language and allows some restrictions that the four freedoms forbid. stallman regards this as a fundamental philosophical error — see software-freedom-vs-open-source.
The framework influenced larry-lessig's creative-commons project, which applied similar thinking to creative works more broadly. The free-as-in-freedom-concept distinction — free as in freedom, not free as in beer — is the popular shorthand for what Freedom 0 through Freedom 3 try to specify precisely.
The four freedoms are the benchmark against which stallman evaluates every license, policy, and software project. Anything that fails on any of the four is, from his perspective, a tool of user subjugation rather than user empowerment.