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It has been suggested that many philosophical theses--physicalism, nominalism, normative naturalism, and so on--should be understood in terms of ground. Against this, Ted Sider has argued that ground is ill-suited for this purpose. Here, Dasgupta develops Sider's objection and offers a response.

The Principle of Sufficient Reason states that everything has an explanation. But different notions of explanation yield different versions of this principle. Here a version is formulated in terms of the notion of a \"grounding\" explanation. Its consequences are then explored, with particular emphasis on the fact that it implies necessitarianism, the view that every truth is necessarily true. Finally, the principle is defended from a number of objections, including objections to necessitarianism. The result is a defense of a \"rationalist\" metaphysics, one that constitutes an alternative to the contemporary dogmas that some aspects of the world are \"metaphysically brute\" and that the world could in so many ways have been different.

Arsenic accumulation in seafloor cold seeps is poorly understood. Here, we investigate the interplay between arsenic and methane biogeochemical cycles at the Haima cold seep, South China Sea. Geochemical analyses showed elevated arsenic levels in seep sediments, primarily as sulfide‐bound forms, with strong correlations between dissolved arsenic and methane oxidation proxies (DIC, R2 = 0.64, p < 0.05; δ13CDIC, R2 = 0.86, p < 0.05). Metagenomic sequencing revealed diverse functional genes related to arsenic‐, methane‐ and sulfur cycling, including co‐occurrence of arrA and dsrA in sulfate‐reducing bacteria Desulfobacterota, which are symbionts of Anaerobic Methane Oxidizing Archaea. We propose that anaerobic oxidation of methane (AOM) and the enhanced “metal particle shuttle effect,” both associated with methane release, drive arsenic sequestration. Cold seeps may sequester 0.04–1.81 × 103 kg arsenic annually. These finding highlights cold seeps are hotspots of arsenic cycling with implications for oceanic arsenic chemistry.

Symmetries in physics are a guide to reality. That much is well known. But what is less well known is why symmetry is a guide to reality. What justifies inferences that draw conclusions about reality from premises about symmetries? I argue that answering this question reveals that symmetry is an epistemic notion twice over. First, these inferences must proceed via epistemic lemmas: premises about symmetries in the first instance justify epistemic lemmas about our powers of detection, and only from those epistemic lemmas can we draw conclusions about reality. Second, in order to justify those epistemic lemmas, the notion of symmetry must be defined partly in epistemic terms.

Much recent metaphysics is built around notions such as naturalness, fundamentality, grounding, dependence, essence, and others besides. In this article I raise a problem for this kind of metaphysics, the “problem of missing value.” I survey a number of possible solutions to the problem and find them all wanting. This suggests a return to a kind of Goodmanian view that the world is a structureless mess onto which we project our own categorizations, not something with categories already built in.

This paper argues that ground is irreducibly plural: a group of facts can be grounded together, as a collective, even though no member of the group has a ground on its own. This kind of plural grounding is applied to the metaphysics of individuals and quantities, yielding a “structuralist” view in each case. Some more general implications of plural grounding are also discussed.

Hunger makes Drosophila larvae move faster in search of food. Koon and colleagues show that starvation increases the branching of octopaminergic motoneurons' axonal terminal arbors, driven by octopamine released from these same motoneurons. The increased locomotor activity of starved larvae requires octopaminergic signaling. Adrenergic signaling has important roles in synaptic plasticity and metaplasticity. However, the underlying mechanisms of these functions remain poorly understood. We investigated the role of octopamine, the invertebrate counterpart of adrenaline and noradrenaline, in synaptic and behavioral plasticity in Drosophila . We found that an increase in locomotor speed induced by food deprivation was accompanied by an activity- and octopamine-dependent extension of octopaminergic arbors and that the formation and maintenance of these arbors required electrical activity. Growth of octopaminergic arbors was controlled by a cAMP- and CREB-dependent positive-feedback mechanism that required Octβ2R octopamine autoreceptors. Notably, this autoregulation was necessary for the locomotor response. In addition, octopamine neurons regulated the expansion of excitatory glutamatergic neuromuscular arbors through Octβ2Rs on glutamatergic motor neurons. Our results provide a mechanism for global regulation of excitatory synapses, presumably to maintain synaptic and behavioral plasticity in a dynamic range.

Normative non-naturalism is the view that some normative properties are irreducible and non-natural. Against this view, it has been objected that non-natural properties like these would have no ‘normative authority’ over us. This paper formulates the objection in a particular way, and argues that standard non-naturalist responses are inadequate. The formulation here is distinctive in so far as it rests on no controversial principles connecting normative judgement and motivation.

Volcanic ash is a major component of marine sediment, but its effect on the deep-sea carbon cycle remains enigmatic. Here, we analyzed mineralogical compositions and glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in submarine tuffs from the Mariana Trough, demonstrating a fraction of organic carbon associated with volcanic ash is produced in situ. This likely derives from chemolithotrophic communities supported by alteration of volcanic material. Tuff GDGTs are characterized by enrichment of branched GDGTs, as in chemolithotrophic communities. Scanning electron microscope, Raman spectrum and nano secondary ion mass spectrometry analysis demonstrates organic carbon exists around secondary heamatite veins in the altered mafic minerals, linking mineral alteration to chemolithotrophic biosynthesis. We estimate organic carbon production of between 0.7 − 3.7 × 10 11  g if all the chemical energy produced by ash alteration was fully utilized by microorganisms. Therefore, the chemolithotrophic ecosystem maintained by ash alteration likely contributes considerably to organic carbon production in the seafloor.