Tort defences are generally neglected; and given the considerable role they play in defamation, this is probably the cause of action where this neglect matters most. The law of defamation recognises a dozen or so defences: at first sight the list looks like a hotchpotch of unrelated doctrines. This paper is an attempt to reduce them to a few guiding principles. Taking as its starting point the definition of the cause of action as an injury to the claimant’s reputation, it argues that those doctrines fall into three classes: (i) defences which exclude unlawfulness, ie justify the injury on the basis that it was inflicted in pursuance of a right or liberty granted to the defendant; (ii) defences which exclude blameworthiness, ie excuse the defendant because he was not at fault for causing the injury; (iii) defences which relieve the defendant of liability despite the injury being both non iure and negligent: that last group, not being underpinned by already recognised principles, deserves particular scrutiny. Part of it really is concerned with the rule of repetition, which needs to be qualified by the recognition of a defence of ‘warranted republication’; the remainder ought to be abolished, being an anachronistic hangover from the old requirement of malice.