 Naïve HD can also be enriched by the notion of simplicity. According to this view, the naïve HD clause for confirmation is too weak because \(h\wedge k\) must be a simple (enough), unified way to account for evidence \(e\). A classic reference for the simplicity view is Newton’s first law of philosophizing in the Principia (“admit no more causes of natural things than such as are both true and sufficient to explain their appearances”), echoing very closely Ockham’s razor. This basic idea has never lost its appeal—even up to recent times (see, e.g., Quine and Ullian 1970, 69 ff.; Sober 1975; Zellner, Keuzenkamp, and McAleer 2002; Scorzato 2013).