2,893 research outputs found
Counterfactual Skepticism and Multidimensional Semantics
It has recently been argued that indeterminacy and indeterminism make most ordinary counterfactuals false. I argue that a plausible way to avoid such counterfactual skepticism is to postulate the existence of primitive modal facts that serve as truth-makers for counterfactual claims. Moreover, I defend a new theory of âmightâ counterfactuals, and develop assertability and knowledge criteria to suit such unobservable âcounterfactsâ
Population Ethics under Risk
Population axiology concerns how to evaluate populations in terms of their moral goodness, that is, how to order populations by the relations âis better thanâ and âis as good asâ. The task has been to find an adequate theory about the moral value of states of affairs where the number of people, the quality of their lives, and their identities may vary. So far, this field has largely ignored issues about uncertainty and the conditions that have been discussed mostly pertain to the ranking of risk-free outcomes. Most public policy choices, however, are decisions under uncertainty, including policy choices that affect the size of a population. Here, we shall address the question of how to rank population prospectsâthat is, alternatives that contain uncertainty as to which population they will bring aboutâby the relations âis better thanâ and âis as good asâ. We start by illustrating how well-known population axiologies can be extended to population prospect axiologies. And we show that new problems arise when extending population axiologies to prospects. In particular, traditional population axiologies lead to prospect-versions of the problems that they praised for avoiding in the risk-free settings. Finally, we identify an intuitive adequacy condition that, we contend, should be satisfied by any population prospect axiology, and show how given this condition, the impossibility theorems in population axiology can be extended to (non-trivial) impossibility theorems for population prospect axiology
How valuable are chances?
Chance Neutrality is the thesis that, conditional on some proposition being true (or being false), its chance of being true should be a matter of practical indifference. The aim of this paper is to examine whether Chance Neutrality is a requirement of rationality. We prove that given Chance Neutrality, the Principal Principle entails a thesis called Linearity; the centrepiece of von Neumann and Morgensternâs expected utility theory. With this in mind, we argue that the Principal Principle is a requirement of practical rationality but that Linearity is not; and hence, that Chance Neutrality is not rationally required
How valuable are chances?
Chance Neutrality is the thesis that, conditional on some proposition being true (or being false), its chance of being true should be a matter of practical indifference. The aim of this paper is to examine whether Chance Neutrality is a requirement of rationality. We prove that given Chance Neutrality, the Principal Principle entails a thesis called Linearity; the centrepiece of von Neumann and Morgensternâs expected utility theory. With this in mind, we argue that the Principal Principle is a requirement of practical rationality but that Linearity is not; and hence, that Chance Neutrality is not rationally required
Counterfactual Desirability
The desirability of what actually occurs is often influenced by what could have been. Preferences based on such value dependencies between actual and counterfactual outcomes generate a class of problems for orthodox decision theory, the best-known perhaps being the so-called Allais Paradox. In this paper we solve these problems by extending Richard Jeffrey's decision theory to counterfactual prospects, using a multidimensional possible-world semantics for conditionals, and showing that preferences that are sensitive to counterfactual considerations can still be desirability maximising. We end the paper by investigating the conditions necessary and sufficient for a desirability function to be an expected utility. It turns out that the additional conditions imply highly implausible epistemic principles
Hierarchical Finite State Machines for Efficient Optimal Planning in Large-scale Systems
In this paper, we consider a planning problem for a hierarchical finite state
machine (HFSM) and develop an algorithm for efficiently computing optimal plans
between any two states. The algorithm consists of an offline and an online
step. In the offline step, one computes exit costs for each machine in the
HFSM. It needs to be done only once for a given HFSM, and it is shown to have
time complexity scaling linearly with the number of machines in the HFSM. In
the online step, one computes an optimal plan from an initial state to a goal
state, by first reducing the HFSM (using the exit costs), computing an optimal
trajectory for the reduced HFSM, and then expand this trajectory to an optimal
plan for the original HFSM. The time complexity is near-linearly with the depth
of the HFSM. It is argued that HFSMs arise naturally for large-scale control
systems, exemplified by an application where a robot moves between houses to
complete tasks. We compare our algorithm with Dijkstra's algorithm on HFSMs
consisting of up to 2 million states, where our algorithm outperforms the
latter, being several orders of magnitude faster.Comment: Accepted to ECC 202
Fairness and risk attitudes
According to a common judgement, a social planner should often use a lottery to decide which of two people should receive a good. This judgement undermines one of the best-known arguments for utilitarianism, due to John C. Harsanyi, and more generally undermines axiomatic arguments for utilitarianism and similar views. In this paper we ask which combinations of views about (a) the social plannerâs attitude to risk and inequality, and (b) the subjectsâ attitudes to risk are consistent with the aforementioned judgement. We find that the class of combinations of views that can plausibly accommodate this judgement is quite limited. But one theory does better than others: the theory of chance-sensitive utility
First Light of Engineered Diffusers at the Nordic Optical Telescope Reveal Time Variability in the Optical Eclipse Depth of WASP-12b
We present the characterization of two engineered diffusers mounted on the
2.5 meter Nordic Optical Telescope, located at Roque de Los Muchachos, Spain.
To assess the reliability and the efficiency of the diffusers, we carried out
several test observations of two photometric standard stars, along with
observations of one primary transit observation of TrES-3b in the red (R-band),
one of CoRoT-1b in the blue (B-band), and three secondary eclipses of WASP-12b
in V-band. The achieved photometric precision is in all cases within the
sub-millimagnitude level for exposures between 25 and 180 seconds. Along a
detailed analysis of the functionality of the diffusers, we add a new transit
depth measurement in the blue (B-band) to the already observed transmission
spectrum of CoRoT-1b, disfavouring a Rayleigh slope. We also report variability
of the eclipse depth of WASP-12b in the V-band. For the WASP-12b secondary
eclipses, we observe a secondary-depth deviation of about 5-sigma, and a
difference of 6-sigma and 2.5-sigma when compared to the values reported by
other authors in similar wavelength range determined from Hubble Space
Telescope data. We further speculate about the potential physical processes or
causes responsible for this observed variabilityComment: 11 pages, 9 figure
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