The question of interpolations in the Pauline letters continues to provoke debate. Recent years have seen numerous attempts to identify particular passages as non-Pauline and occasional arguments for extensive interpolating throughout the letters. Nevertheless, as Victor Paul Furnish has pointed out, ‘no general scholarly agreement’ has emerged ‘on the probability, or even the plausibility, of any of these hypotheses about … interpolations’. A major problem is the fact that most of the discussion has focused directly upon individual passages, with little or no systematic attention to such preliminary matters as the burden of proof in the identification of interpolations or specific techniques or criteria that might aid in identifying interpolations. Although the burden-of-proof question and the question of criteria are clearly related, and both are crucial, it is possible to separate them for purposes of discussion, and it can even be argued that the former question is, at least logically, prior to the latter. Thus, the purpose of this paper is to raise only the burden-of-proof question; that of criteria must be reserved for treatment in a different context.