Since its founding nearly 15 years ago, Sonos has amassed a devoted following among audio enthusiasts for its high-end, WiFi-connected speakers. But now its business is endangered by a new breed of speakers powered by artificial intelligence assistants from the likes of Google and Amazon. They're starting to eat into the company's bottom line. In the midst of that change, Sonos cofounder John MacFarlane is stepping down as CEO after leading the company since 2002. Sonos president Patrick Spence will be taking over as CEO.

After 14 years at the helm, Sonos CEO and co-founder John MacFarlane has stepped down. He has also resigned from the company's board or directors, but will remain with Sonos to work on other projects and serve as a mentor to employees. MacFarlane's transition is the latest in a handful of personnel moves that began last year. Sonos announced layoffs last March shortly before product head Marc Whitten left the company. Former president and chief commercial officer Patrick Spence will take over as CEO.

A good explanation among many others of logical consequence is that given a possibly empty set of assumptions A that are said to entail x, written A x, one is bound to believe x whenever it is the case that she believes the conjunction of all elements of A. This explanation shows a weak correspondence with the Tarskian semantic definition of logical consequence, according to which A entails x if and only if x is true under all interpretations (models) that make all elements of A true. But the relevant term here is "bound" ("is obliged to"), and the talk is of a normative conception of logical consequence. But where does this command come from? To understand some of the implications of what we call here a normative account of logical consequence, we will consider a notion which is not very well understood until the present day: that of "defeasible subsumption". To grasp this notion, it suffices to consider the following example.