Frank Van Dun (born February 22, 1947, Antwerp) is a Belgian philosopher of law and classical liberal natural law theorist. He is associated with the law faculty of the University of Ghent. In 2013 he was awarded the Prize for Liberty by the Flemish classical-liberal think tank Libera!.

Van Dun published his book Het Fundamenteel Rechtsbeginsel (Dutch for The Fundamental Principle of Law) in 1983, in which he argued that a rationally convincing answer to the question "What is law?" can only be found by respecting dialogue and argumentation. He is thus an adherent of argumentation ethics. Based on this premise, Van Dun argues that every natural person (individual) has a lawful claim on his life, freedom and property. This claim is absolute, insofar it does not prohibit the equivalent claims of other natural persons, i.e. insofar as argumentation is respected.

Van Dun clearly distinguishes the lawful (ius) and the legal (lex). In his view, Western positive law systems reduce people to human resources, artificial persons with merely legal status. Positive law defines the legal but can only be lawful insofar as individuals have full secession rights from the institutional framework that is making said positive law. It logically follows that no judge can be forced upon a person who is willing to search a lawful solution for any conflict.

Van Dun claims that the correct interpretation of the non-aggression principle (NAP) is praxeological rather than physical, because property is a "means of action". He thus claims freedom before property instead of freedom as property.^{[citation needed]} This implies that it's not necessarily only the last action in the chain of social causations that is unlawful. Consider the following examples:

• With regard to land encirclement, a praxeological NAP could imply a "freedom proviso" when the encircling land owner refuses to discuss a reasonable solution.
• With regard to copyrights, a praxeological NAP implies that the use of one's signature (as an expression of one's body as "means of action") could reasonably be considered more important than the physical freedom of exactly copying another person's signature with one's paper and ink.
• With regard to freedom of speech, a praxeological NAP could imply that it is unlawful for an individual to order an unlawful act, e.g. a general ordering a murder of someone willing to seek lawful solutions.

The freedom before property interpretation of the NAP is not widely accepted within the libertarian community. For example, Walter Block adheres to the freedom as property interpretation.^[1]

The Belgian newspaper Le Soir reported on 8 June 2012, that between 1988 and 2000, Belgian scientists Van Dun and Marcel Javeau were paid by the tobacco lobby, through the group 'Associates for Research in the Science of Enjoyment' (ARISE).^[3] Van Dun responded in the Belgian Eos-magazine^[4] that while indeed he gave two presentations for ARISE in which he presented his visions, he wasn't paid to do so and he never was a member of ARISE. However, the Legacy Tobacco Documents Library contains a document^[5] that lists Van Dun as an "associate".

• Het fundamenteel rechtsbeginsel (‘The Fundamental Principle of Law’) (1983) (Dutch 2008 PDF version^{[permanent dead link]})
• Crash en Depressie (1988) (‘Crash and Depression’) ISBN 90-72435-01-X
• De utopische verleiding (‘The Utopian Enticement’), with Hans Crombag, 1997, ISBN 90-254-2466-X
• Mens, burger, fiscus (‘Man, Citizen, Taxes’, 2000) ISBN 90-423-0125-2