Synthese

The feeling of grip: novelty, error dynamics, and the predictive brain Abstract According to the free energy principle biological agents resist a tendency to disorder in their interactions with a dynamically changing environment by keeping themselves in sensory and physiological states that are expected given their embodiment and the niche they inhabit (Friston in Nat Rev Neurosci 11(2):127–138, 2010. doi:10.1038/nrn2787). Why would a biological agent that aims at minimising uncertainty in its encounters with the world ever be motivated to seek out novelty? Novelty for such an agent would arrive in the form of sensory and physiological states that are unexpected. Such an agent ought therefore to avoid novel and surprising interactions with the world one might think. Yet humans and many other animals find play and other forms of novelty-seeking and exploration hugely rewarding. How can this be understood in frameworks for studying the mind that emphasise prediction error minimisation? This problem has been taken up in recent research concerned with epistemic action—actions an agent engages in to reduce uncertainty. However that work leaves two questions unanswered, which it is the aim of our paper to address. First, no account has been given yet of why it should feel good to the agent to engage the world playfully and with curiosity. Second an appeal is made to precision-estimation to explain epistemic action, yet it remains unclear how precision-weighting works in action more generally, or active inference. We argue that an answer to both questions may lie in the bodily states of an agent that track the rate at which free energy is being reduced. The recent literature on the predictive brain has connected the valence of emotional experiences to the rate of change in the reduction of prediction error (Joffily and Coricelli in PLoS Comput Biol 9(6):e1003094, 2013. doi:10.1371/journal.pcbi.1003094; Van de Cruys, in Metzinger and Wiese (eds) Philosophy and predictive processing, vol 24, MIND Group, Frankfurt am Main, 2017. doi:10.15502/9783958573253). In this literature valenced emotional experiences are hypothesised to be identical with changes in the rate at which prediction error is reduced. Experiences are negatively valenced when overall prediction error increases and are positively valenced when the sum of prediction errors decrease. We offer an ecological-enactive interpretation of the concept of valence and its connection to rate of change of prediction error. We show how rate of change should be understood in terms of embodied states of affordance-related action readiness. We then go on to apply this ecological-enactive account of error dynamics to provide an answer to the first question we have raised: It may explain why it should feel good to an agent to be curious and playful. Our ecological-enactive account also allows us to show how error dynamics may provide an answer to the second question we have raised regarding how precision-weighting works in active inference. An agent that is sensitive to rates of error reduction can tune precision on the fly. We show how this ability to tune precision on the go can allow agents to develop skills for adapting better and better to the unexpected, and search out opportunities for resolving uncertainty and progressing in its learning.

The challenge of many logics: a new approach to evaluating the role of ideology in Quinean commitment Abstract Can Quine's criterion for ontological commitment be comparatively applied across different logics? If so, how? Cross-logical evaluations of discourses are central to contemporary philosophy of mathematics and metaphysics. The focus here is on the influential and important arguments of George Boolos and David Lewis that second-order logic and plural quantification don't incur additional ontological commitments over and above those incurred by first-order quantifiers. These arguments are challenged by the exhibition of a technical tool—the truncation-model construction of notational equivalents—that compares the ontological role and increased expressive strength of non-first-order ideology to first-order ideology.

Possible predicates and actual properties Abstract In "Properties and the Interpretation of Second-Order Logic" (Hale, Philos Math 21:133–156, 2013) Bob Hale develops and defends a deflationary conception of properties where a property with particular satisfaction conditions actually (and in fact necessarily) exists if and only if it is possible that a predicate with those same satisfaction conditions exists. He argues further that, since our languages are finitary, there are at most countably infinitely many properties and, as a result, the account fails to underwrite the standard semantics for second-order logic. Here a more lenient version of the view is explored, which allows for the possibility of countably infinite predicates understood as the product of linguistic supertasks. This enriched deflationist account of properties—the Infinitary Deflationary Conception of Existence—supports the standard semantics for models with countable first-order domains, and allows one to prove the categoricity of the second-order Peano axioms.

A psychologistic theory of metaphysical explanation Abstract Many think that sentences about what metaphysically explains what are true iff there exist grounding relations. This suggests that sceptics about grounding should be error theorists about metaphysical explanation. We think there is a better option: a theory of metaphysical explanation which offers truth conditions for claims about what metaphysically explains what that are not couched in terms of grounding relations, but are instead couched in terms of, inter alia, psychological facts. We do not argue that our account is superior to grounding-based accounts. Rather, we offer it to those already ill-disposed towards grounding.

Bolzano and Kim on grounding and unification Abstract It is sometimes mentioned that Bernard Bolzano's work on grounding anticipates many insights of the current debate on metaphysical grounding. The present paper discusses a certain part of Bolzano's theory of grounding that has thus far not been discussed in the literature. This part does not so much anticipate what are nowadays common assumptions about grounding, but rather goes beyond them. Central to the discussion will be a thesis of Bolzano's by which he tries to establish a connection between grounding and (deductive) unification. The paper spells out this thesis in detail and discusses the assumptions on which it rests. Next to this mainly historical aim, the paper also presents reasons why philosophers who are not interested in the historical Bolzano should find the thesis interesting by relating it to a certain view on unification and explanation that has been put forward by Kim. A final part of the paper provides a critical evaluation of the thesis against the background of current accounts of grounding.

Aggregating incoherent agents who disagree Abstract In this paper, we explore how we should aggregate the degrees of belief of a group of agents to give a single coherent set of degrees of belief, when at least some of those agents might be probabilistically incoherent. There are a number of ways of aggregating degrees of belief, and there are a number of ways of fixing incoherent degrees of belief. When we have picked one of each, should we aggregate first and then fix, or fix first and then aggregate? Or should we try to do both at once? And when do these different procedures agree with one another? In this paper, we focus particularly on the final question.

Ambiguous signals, partial beliefs, and propositional content Abstract As the content of propositional attitudes, propositions are usually taken to help explain the behavior of rational agents. However, a closer look at signaling games suggests otherwise: rational agents often acquire partial beliefs, and many of their signals are ambiguous. Signaling games also suggest that it is rational for agents to mix their behavior in response to partial beliefs and ambiguous signals. But as I show in this paper, propositions cannot help explain the mixing behavior of rational agents: to explain mixing behavior, we need a probabilistic notion of content. I also show that a probabilistic notion of content renders propositions explanatorily idle in the case of unambiguous signals and full beliefs as well. My suggestion is thus that we should abandon propositions in explanations of rational behavior and adopt instead a probabilistic notion of content. The notion of probabilistic content ultimately provides a simpler framework for explanations of rational behavior than the notion of propositional content.

Evolutionary debunking: the Milvian Bridge destabilized Abstract Recent literature has paid attention to a demarcation problem for evolutionary debunking arguments. This is the problem of asking in virtue of what regulative metaepistemic norm evolutionary considerations either render a belief justified, or debunk it as unjustified. I examine the so-called 'Milvian Bridge principle' (cf. Griffiths and Wilkins (in: Maclaurin, Dawes (eds) A new science of religion, Routledge, New York, 2012; Sloan, McKenny, Eggelson (eds) Darwin in the 21st century: nature, humanity, and God, University Press, Notre Dame, 2015)), which offers exactly such a called for regulative metaepistemic norm. The Milvian Bridge principle suggests that the metaepistemic norm is: adaptive reliability for truth of cognitive processes that the existence of corresponding truth-making facts evolutionary theory justifies. I argue that the Milvian Bridge principle is problematic on a number of counts, something that is shown via spiraling 'companions in guilt arguments'. Finally, I consider 'the core reductionist objection' to the critique of the Milvian Bridge principle and offer a response. I conclude that the Milvian Bridge principle is destabilized.

The bifurcated conception of perceptual knowledge: a new solution to the basis problem for epistemological disjunctivism Abstract Epistemological disjunctivism says that one can know that p on the rational basis of one's seeing that p. The basis problem for disjunctivism says that that can't be since seeing that p entails knowing that p on account of simply being the way in which one knows that p. In defense of their view disjunctivists have rejected the idea that seeing that p is just a way of knowing that p (the \(\hbox {S}_{\mathrm{w}}\hbox {K}\) thesis). That manoeuvre is familiar. In this paper I explore the prospects for rejecting instead the thought that if the \(\hbox {S}_{\mathrm{w}}\hbox {K}\) thesis is true then seeing that p can't be one's rational basis for perceptual knowledge. I explore two strategies. The first situates disjunctivism within the context of a 'knowledge-first' approach that seeks to reverse the traditional understanding of the relationship between perceptual knowledge and justification (or rational support). But I argue that a more interesting strategy situates disjunctivism within a context that accepts a more nuanced understanding of perceptual beliefs. The proposal that I introduce reimagines disjunctivism in light of a bifurcated conception of perceptual knowledge that would see it cleaved along two dimensions. On the picture that results perceptual knowledge at the judgemental level is rationally supported by perceptual knowledge at the merely functional or 'animal' level. This supports a form of disjunctivism that I think is currently off the radar: one that's consistent both with the \(\hbox {S}_{\mathrm{w}}\hbox {K}\) thesis and a commitment to a traditional reductive account of perceptual knowledge.

Second-order logic: properties, semantics, and existential commitments Abstract Quine's most important charge against second-, and more generally, higher-order logic is that it carries massive existential commitments. The force of this charge does not depend upon Quine's questionable assimilation of second-order logic to set theory. Even if we take second-order variables to range over properties, rather than sets, the charge remains in force, as long as properties are individuated purely extensionally. I argue that if we interpret them as ranging over properties more reasonably construed, in accordance with an abundant or deflationary conception, Quine's charge can be resisted. This interpretation need not be seen as precluding the use of model-theoretic semantics for second-order languages; but it will preclude the use of the standard semantics, along with the more general Henkin semantics, of which it is a special case. To that extent, the approach I recommend has revisionary implications which some may find unpalatable; it is, however, compatible with the quite different special case in which the second-order variables are taken to range over definable subsets of the first-order domain, and with respect to such a semantics, some important metalogical results obtainable under the standard semantics may still be obtained. In my final section, I discuss the relations between second-order logic, interpreted as I recommend, and a strong version of schematic ancestral logic promoted in recent work by Richard Heck. I argue that while there is an interpretation on which Heck's logic can be contrasted with second-order logic as standardly interpreted, when it is so interpreted, its differences from the more modest form of second-order logic I advocate are much less substantial, and may be largely presentational.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
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alsfakia@gmail.com