This month’s episode of “What Is X?” asks a suitably grand question for the end of the year and for the end of Season 2: What is being? To help him figure it out once and for all (or to at least lessen our state of aporia), Justin brings on as his guest Kris McDaniel, a professor of philosophy at Notre Dame and the author of “The Fragmentation of Being.” Though we might find this question intimidating, Kris notes that this is no longer the case today: though fundamental throughout the history of philosophy, it’s now popular to think the nature of being is too simple to spend much time on. To restore the concept to its proper place, Kris and Justin delve into Heidegger, examined here as part of the Aristotelian tradition. (Heideggerians, take note: this is the episode for you.) What is Dasein, anyway? What distinguishes it from the human? And the hardest metaphysical question of all: Why is the man-on-the-street gut-level notion of what being is still so distant from all this Dasein talk? These questions have ethical implications, too: Kris and Justin discuss what kind of effect ontological status might have on our relationships, and what happens if it turns out our own kids are just random aggregates of particles. Also discussed: whether biology alone can disclose the essence of the siphonophore, why God doesn’t care about wheelbarrows, and the risks of spending too much time with Leibniz.