Although ecological theory has historically focused on negative interactions among populations, like competition and predation, ecologists and conservation biologists highlight the significance of interdependence. It is not clear, however, what is asserted in the causal hypothesis that one population is interdependent on others. This essay argues that the most informative causal regularities for representing dependencies are those connecting populations through environmental constraint variables. Interdependence among populations can thus be understood as constraint-mediated dependency relations connected in a circuit.

Aldo Leopold’s land ethic, an extremely influential view in environmental ethics and conservation biology, is committed to the claim that interdependence between humans, other species, and abiotic entities plays a central role in our ethical responsibilities. Thus, a robust understanding of “interdependence” is necessary for evaluating the viability of the land ethic and related views, including ecological ones. I characterize and defend a Leopoldian concept of “interdependence,” arguing that it ought to include both negative and positive causal relations. I also show that strength and type of interdependence can vary with time, space, and context.

Much philosophical attention has been devoted to whether economic models explain and more generally to how scientific models represent. Yet there is an issue more practically important to economics than either of these, which I label the efficiency question: regardless of how exactly models represent, or of whether their role is explanatory or something else, is current modeling practice an efficient way to achieve these goals or should research efforts be redirected? In addition to showing how the efficiency question has been relatively neglected, I give two examples of the kind of analysis it requires.

The Black-Scholes(-Merton) model of options pricing establishes a theoretical relationship between the “fair” price of an option and other parameters characterizing the option and prevailing market conditions. Here I discuss a common application of the model with the following striking feature: the (expected) output of analysis apparently contradicts one of the core assumptions of the model on which the analysis is based. I will present several attitudes one might take toward this situation and argue that it reveals ways in which a “broken” model can nonetheless provide useful (and tradeable) information.

Providing a precise statement of their position has long been a central challenge facing scientific realists. This article draws some morals about how realism ought to be formulated from the renormalization group framework in high-energy physics.

One realist response to the pessimistic meta-induction distinguishes idle theoretical wheels from aspects of successful theories we can expect to persist and espouses realism about the latter. Implementing the response requires a strategy for identifying the distinguished aspects. The strategy I will call renormalization group realism has the virtue of directly engaging the gears of our best current physics—perturbative quantum field theories. I argue that the strategy, rather than disarming the skeptical possibilities evinced by the pessimistic meta-induction, forces them to retreat a level. I also suggest that those skeptical possibilities continue to carry force.

This article examines two cosmological models of quantum gravity (from string theory and loop quantum gravity) to investigate the foundational and conceptual issues arising from quantum treatments of the big bang. While the classical singularity is erased, the quantum evolution that replaces it may not correspond to classical spacetime: it may instead be a nonspatiotemporal region that somehow transitions to a spatiotemporal state. The different kinds of transition involved are partially characterized, the concept of a physical transition without time is investigated, and the problem of empirical incoherence for regions without spacetime is discussed.

Gravitational interactions allowed astronomers to conclude that dark matter rings all luminous galaxies in gigantic halos, but this only accounts for a fraction of the total mass of dark matter believed to exist. Where is the rest? We hypothesize that some of it resides in dark galaxies, pure dark matter halos that either never possessed or have totally lost their baryonic matter. This article explores methodological challenges that arise because of the nature of observation in astrophysics and examines how the blend of observation, simulation, and theory we call the Observing the Invisible approach might make detecting such dark objects possible.