Thursday, 23 January, 2:30 - 4:30
Decision Theory Masterclass (1 of 3), Richard Bradley (LSE)
This masterclass will provide an introduction to the main theory of decision making under uncertainty, covering the Savage and Anscombe-Aumann framework's, the Ellsberg paradox and the debate over the quantification of uncertainty, theories of decision under ignorance and perhaps some of the early alternatives to Savage. The class will not assume any prior knowledge of decision theory but will cover the basics at very high speed. Decision Theory Masterclass 1 slides [pdf]
Thursday, 30 January, 2:30 - 4:30
Ken Binmore (Bristol and UCL, Economics and Philosophy)
"Rational Decisions in Large Worlds"
ABSTRACT: Savage denied that Bayesian decision theory applies in large worlds. A minimal extension of Bayesian decision theory to a large-world context assigns upper and lower probabilities to ambiguous or uncertain events—those to which a single probability cannot be assigned. The orthodox Hurwicz criterion evaluates an ambiguous or uncertain event as a weighted arithmetic mean of its upper and lower probability. The ambiguity or uncertainty aversion reported in experiments on the Ellsberg paradox is then explained by assigning a larger weight to the lower probability of winning than to the upper probability. This paper reviews a possible framework for assessing both the arithmetic Hurwicz criterion and a geometric variant. It then argues that only the case of equal weights satisﬁes appropriate consistency requirements—a result that accords with our own experiments on the Ellsberg paradox. However, the geometric Hurwicz criterion allows another and more severe interpretation of uncertainty aversion that persists even in the case of equal weights.
Thursday, 13 February, 2:30 - 4:30
Decision Theory Masterclass (2 of 3), Katie Steele (LSE)
This 2nd Decision Theory Masterclass pursues a topic that is related but somewhat independent of Decision Theory Masterclasses 1 and 3. The first part will introduce the standard decision theory (expected utility) model for determining the ‘value of information’, or in other words, how much we should be willing to pay (whether in time, money, brainpower or other resources) to pursue new information/evidence, given the decision problems that we face. Philosophical applications of this model will be discussed, and its limitations explored. The second part will shift to the context of severe uncertainty, and what role considerations of the ‘value of information’ may play in debates about rational decision-making in this context.
Thursday, 27 February, 2:30 - 4:30
Charlotte Werndl (LSE)
"On Defining Climate and Climate Change"
This talk analyses the main candidates for a definition of climate and climate change. Five desiderata on a definition of climate are presented: it should be empirically applicable, it should correctly classify different climates, it should not depend on our knowledge, is should be applicable to the past, present and future and it should be mathematically well-defined. Then five definitions are discussed: climate as distribution over time for constant external conditions, climate as distribution over time when the external conditions vary as in reality, climate as distribution over time relative to regimes of varying external conditions, climate as the ensemble distribution for constant external conditions, and climate as the ensemble distribution when the external conditions vary as in reality. The third definition is novel and is introduced as a response to problems with existing definitions. The conclusion is that most definitions encounter serious problems and that the third definition is most promising.
Thursday, 6 March, 2:30 - 4:30
Decision Theory Masterclass (3 of 3), Richard Bradley (LSE)
In this third masterclass I will be presenting the main 'post-Bayesian' models of decision making under uncertainty (ambiguity), including Maximin EU, the 'smooth' model of ambiguity and Bewley's theory of choice under incompleteness. In order to understand the background for these models I will look briefly at the older literature on decision making under ignorance and present the Anscombe-Aumann framework within which much of the contemporary literature works. Decision Theory Masterclass 3 slides [pdf]
Postponed until Summer term:
Discussion of IPCC Working Group 1 Summary for Policymakers
The Intergovernmental Panel on Climate Change (IPCC) recently released the newest report from Working Group 1, the group tasked with assessing 'the physical scientific aspects of the climate system and climate change.' At this meeting we will discuss the Summary for Policymakers (SPM) document that is based on the full report (1500 pages) of Working Group 1. Summary for Policy Makers
Thursday, 24 October, 2:30 - 4:30
Climate Models Masterclass (1 of 3), Roman Frigg (LSE)
The three masterclasses are in effect a crash course in the natural science aspects of climate change. Everybody wishing to understand the basic physics behind climate change and the use of climate models is welcome to attend; no prior knowledge is presupposed. The first lecture explains the earth's energy balance and introduces basic concepts such as the greenhouse effect, radiative forcing, time lags, feedback loops, climate sensitivity and climate variability. The second lecture reviews the empirical evidence for climate change and discusses some sceptical claims. The third lecture introduces climate models and discusses what kinds of uncertainties attach to them.
Climate Models Masterclass 1 slides [pdf]
Thursday, 14 November, 2:30 - 4:30
Climate Models Masterclass (2 of 3), Roman Frigg (LSE)
See Oct 24 meeting for description.
Climate Models Masterclass 2 slides [pdf]
Thursday, 21 November, 3:00 - 4:30
The Classification of Uncertainty, Richard Bradley (LSE)
This meeting will be devoted to a discussion of how different kinds of uncertainty should be classified. Note the time change: 3:00 - 4:30.
Thursday, 5 December, 2:30 - 4:30
Climate Models Masterclass (3 of 3), Roman Frigg (LSE)
See Oct 24 meeting for description.
Climate Models Masterclass 3 slides [pdf]
Thursday, 12 December, 2:30 - 4:30
Discussion of forthcoming papers by Nicholas Stern