 The theory of Bayesian confirmation as relevance indicates when and why the HD idea works: if \(h \wedge k\) (but not \(k\)) entails \(e\), then \(h\) is relevance-confirmed by \(e\) (relative to \(k\)) because the latter increases the probability of the former—provided that \(P(e\mid k) \lt 1\). Admittedly, the meaning of the latter proviso partly depends on how one handles the problem of old evidence. Yet it seems legitimate to say that Bayesian relevance confirmation (unlike the firmness view) retains a key point of ordinary scientific practice which is embedded in HD and yields further elements of clarification. Consider the following illustration.