there is a deficiency in the standard formulation of the deductive-nomological (D-N) model of explanation. On the standard model, one explains by citing laws and initial conditions that jointly explain the explanandum. But in fact the explanans not only should state the laws but also that they are laws or at least consequences of laws. For suppose I wish to explain why Mappy liked one of my buttons. I cite three facts: Mappy is a magpie, all my buttons are shiny and all magpies like shiny things, and on the D-N model I am done. But knowing these three facts and justifiably believing that they explain why Mappy liked one of my buttons is not sufficient for my knowing why Mappy liked one of my buttons. For to know why Mappy liked one of my buttons, I need to know that it is a law or a consequence of a law that magpies like shiny things. Unless I know this, I do not know why Mappy liked one of my buttons. Imagine, after all, someone who knows all the three facts cited but who incorrectly justifiably believes that (a) it is a mere accidental generalization that magpies like shiny things and (b) it is a law of nature that all my buttons are shiny. Such a person knows each of the three facts, but does not know why Mappy liked one of my buttons. Therefore, we should take it as part of the explanans that it is a law that magpies like shiny things.