Free Speech and Justified True Belief

59 Pages Posted: 25 Jan 2019

Date Written: January 15, 2019


Law often prioritizes justified true beliefs. Evidence, even if probative and correct, must have a proper foundation. Expert witness testimony must be the product of reliable principles and methods. Prosecutors are not permitted to trick juries into convicting a defendant, even if that defendant is truly guilty. Judges’ reasons, and not just the correctness of their holdings, are the engines of precedent. Lawyers are, in short, familiar with the notion that one must be right for the right reasons.

And yet the standard epistemic theory of the First Amendment—that the marketplace of ideas is the “best test of truth”—has generally focused on truth alone, as if all true beliefs must be treated equally. This thin account leaves the epistemic theory vulnerable to withering criticism, especially in a “post-truth” era.

This Article suggests that the epistemic theory of the First Amendment might be reframed around a different value: not truth alone, but knowledge. Beginning with the tripartite definition of knowledge as justified true belief, philosophers from Plato until the present day have tried to account for what makes knowledge distinct and distinctly valuable. And in many ways law, too, already accounts for the existence and value of justifications, not just true beliefs. Identifying and exploring those threads of constitutional theory and doctrine can help provide a richer account of the cognitive First Amendment at a time when it is sorely needed. Doing so can also help resolve thorny doctrinal problems like those involving professional speech and institutional deference.

Keywords: First Amendment, free speech, epistemology, knowledge, sociology, marketplace of ideas, professions, Plato

Suggested Citation

Blocher, Joseph, Free Speech and Justified True Belief (January 15, 2019). Duke Law School Public Law & Legal Theory Series No. 2019-6, Available at SSRN: or

Joseph Blocher (Contact Author)

Duke University School of Law ( email )

210 Science Drive
Box 90362
Durham, NC 27708
United States

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