This article explores three ways in which physics may involve counterpossible reasoning. The first way arises when evaluating false theories: to say what the world would be like if the theory were true, we need to evaluate counterfactuals with physically impossible antecedents. The second way relates to the role of counterfactuals in characterizing causal structure: to say what causes what in physics, we need to make reference to physically impossible scenarios. The third way is novel: to model metaphysical dependence in physics, we need to consider counterfactual consequences of metaphysical impossibilities. Physics accordingly bears substantial and surprising counterpossible commitments.

Quantum field theories containing massless particles are divergent not just in the ultraviolet but also in the infrared. Infrared divergences are typically regarded as less conceptually problematic than ultraviolet divergences because there is a cancellation mechanism that renders measurable physical observables such as decay rates and cross-sections infrared finite. In this article, I scrutinize the restriction to measurable physical observables that is required to arrive at infrared finite results. I argue that the restriction does not necessitate a retreat to operationalism about the meaning of the theory, but it does call attention to underappreciated features of the infrared regime.

There is a tension in Emilie Du Châtelet’s thought on mathematics. The objects of mathematics are ideal or fictional entities; nevertheless, mathematics is presented as indispensable for an account of the physical world. After outlining Du Châtelet’s position, and showing how she departs from Christian Wolff’s pessimism about Newtonian mathematical physics, I show that the tension in her position is only apparent. Du Châtelet has a worked-out defense of the explanatory and epistemic need for mathematical objects, consistent with their metaphysical nonfundamentality. I conclude by sketching how Du Châtelet’s conception of mathematical indispensability differs interestingly from many contemporary approaches.

String theory reduces to general relativity in appropriate regimes. Huggett and Vistarini have given an account of this reduction that includes a deflationary thesis about symmetry: although the usual derivation of general relativity from string theory appeals to a premise about the theory’s symmetry, Huggett and Vistarini argue that this premise plays no logical role. In this article I disagree with their deflationary thesis and argue that their analysis is based on a popular but flawed conception of the interaction between symmetry and quantization. I argue that a better conception recognizes a distinction between ordinary, broken, and anomalous symmetries.

Some argue that time’s causal arrow is grounded in an underlying thermodynamic asymmetry. Often, this is tied to Humean skepticism that causes produce their effects, in any robust sense of ‘produce’. Conversely, those who advocate stronger notions of natural necessity often reject thermodynamic reductions of time’s causal arrow. Against these traditional pairings, I argue that ‘reduction-plus-production’ is coherent. Reductionists looking to invoke robust production can insist that there are metaphysical constraints on the signs of objects’ velocities in any state, given other—including far later—states’ properties. The Past Hypothesis may thus be a metaphysical condition, not a physical law.

Programs in quantum gravity often claim that time emerges from fundamentally timeless physics. In the semiclassical time program, time arises only after approximations are taken. Here we ask what justifies taking these approximations and show that time seems to sneak in when answering this question. This raises the worry that the approach is either unjustified or circular in deriving time from no-time.

Evolutionary accounts of morality consider behavior in rather simple scenarios. Evolutionary work on fairness focuses on the division of a windfall and, importantly, assumes that the positions of those involved are entirely symmetric. I consider more complicated strategic settings and find that there is a strong tendency for evolution to produce divisions consistent with the so-called Nash bargaining solution. I also uncover the evolutionary importance of comprehensiveness, an often-overlooked feature of division problems.

In this article I argue that we should pay extra attention to the ecological dimension of natural selection. By this I mean that we should view natural selection primarily as acting on the outcomes of the interactions organisms have with their environment, which influences their relative reproductive output. A consequence of this view is that natural selection is not (directly) sensitive to what system of inheritance ensures reoccurrences of organism-environment interactions over generations. I end by showing the consequences of this view when looking at how processes like niche construction and the Baldwin effect relate to natural selection.

At the beginning of the twentieth century, the French philosopher of science Edmond Goblot wrote three prescient papers on function and teleology. He advanced the remarkable thesis that functions are, as a matter of conceptual analysis, selected effects. He also argued that “selection” must be understood broadly to include both evolutionary natural selection and intelligent design. Here, I do three things. First, I give an overview of Goblot’s thought. Second, I identify his core thesis about function. Third, I argue that, despite its ingenuity, Goblot’s expansive construal of function cannot be right. Still, Goblot deserves long-overdue credit for his work.

Living fossils, taxa with similar members now and in the deep past, have recently come under scrutiny. Those who think the concept should be retained have argued for its epistemic and normative utility. This article extends the epistemic utility of the living fossils concept to include ways in which a taxon’s living fossil status can serve as evidence for other claims about that taxon. I will use insights from developmental biology to refine these claims. Insofar as these considerations demonstrate the epistemic utility of the living fossils concept, they support retaining the concept and using it in biological research.

Researchers of language origins typically try to explain how compositional communication might evolve to bridge the gap between animal communication and natural language. However, as an explanatory target, compositionality has been shown to be problematic for a gradualist approach to the evolution of language. In this article, I suggest that reflexivity provides an apt and plausible alternative target that does not succumb to the problems that compositionality faces. I further explain how protoreflexivity, which depends on functional reference, gives rise to complex communication systems via modular composition.

The origin of human cooperation poses an evolutionary puzzle. In order for cooperation to evolve, our Pleistocene ancestors must have overcome the free rider problem, in which noncooperators reap the benefits of cooperation without paying the costs. Cultural group selection accounts offer a potential solution to this problem. In this article, I evaluate Boyd and Richerson’s influential account. I argue that it cannot explain the evolutionary origins of human cooperation because it presupposes cooperative behaviors among our Pleistocene ancestors. Although Boyd and Richerson’s account may explain the expansion of cooperation in hominin evolution, it cannot explain how cooperative behaviors first emerged.