According to Agrippa's trilemma, an attempt to justify something leads to either infinite regress, circularity, or dogmatism. This essay examines whether and to what extent the trilemma applies to ethics. There are various responses to the trilemma, such as foundationalism, coherentism, contextualism, infinitism, and German idealism. Examining those responses, the essay shows that the trilemma applies at least to rational justification of contentful moral beliefs. This means that rationalist ethics based on any contentful moral belief are rationally unjustifiable.

This article sketches a theory of objective probability focusing on nomic probability, which is supposed to be the kind of probability figuring in statistical laws of nature. The theory is based upon a strengthened probability calculus and some epistemological principles that formulate a precise version of the statistical syllogism. It is shown that from this rather minimal basis it is possible to derive theorems comprising (1) a theory of direct inference, and (2) a theory of induction. The theory of induction (...) is not of the familiar Bayesian variety, but consists of a precise version of the traditional Nicod Principle and its statistical analogues. (shrink)

Imagine yourself sitting on your front porch, sipping your morning coffee and admiring the scene before you. You see trees, houses, people, automobiles; you see a cat running across the road, and a bee buzzing among the flowers. You see that the flowers are yellow, and blowing in the wind. You see that the people are moving about, many of them on bicycles. You see that the houses are painted different colors, mostly earth tones, and most are one-story but a (...) few are two-story. It is a beautiful morning. Thus the world interfaces with your mind through your senses. There is a strong intuition that we are not disconnected from the world. We and the other things we see around us are part of a continuous whole, and we have direct access to them through vision, touch, etc. However, the philosophical tradition tries to drive a wedge between us and the world by insisting that the information we get from perception is the result of inference from indirect evidence that is about how things look and feel to us. The philosophical problem of perception is then to explain what justifies these inferences. We will focus on visual perception. Figure one presents a crude diagram of the cognitive system of an agent capable of forming beliefs on the basis of visual perception. Cognition begins with the stimulation of the rods and cones on the retina. From that physical input, some kind of visual processing produces an introspectible visual image. In response to the production of the visual image, the cognizer forms beliefs about his or her surroundings. Some beliefs the perceptual beliefs are formed as direct responses to the visual input, and other beliefs are inferred from the perceptual beliefs. The perceptual beliefs are, at the very least, caused or causally influenced by having the image. This is signified by the dashed arrow marked with a large question mark. We will refer to this as the mystery link. Figure one makes it apparent that in order to fully understand how knowledge is based on perception, we need three different theories.. (shrink)

OSCAR is a fully implemented architecture for a cognitive agent, based largely on the author’s work in philosophy concerning epistemology and practical cognition. The seminal idea is that a generally intelligent agent must be able to function in an environment in which it is ignorant of most matters of fact. The architecture incorporates a general-purpose defeasible reasoner, built on top of an efficient natural deduction reasoner for first-order logic. It is based upon a detailed theory about how the various aspects (...) of epistemic and practical cognition should interact, and many of the details are driven by theoretical results concerning defeasible reasoning. The architecture is easily extensible by changing the set of inference schemes supplied to the reasoner. Existing inference schemes handle many kinds of epistemic cognition, including reasoning from perceptual input, causal reasoning and the frame problem, and reasoning defeasibly about probabilities. Work is underway to implement a system of defeasible decisiontheoretic planning. (shrink)

Philosophy and Phenomenological Research, EarlyView.

This chapter states the contrast between presumptivism about testimonial warrant (often called anti-reductionism) and strict reductionism (associated with Hume) about testimonial warrant. Presumptivism sees an analogy with modest foundationalism about perceptual warrant. Strict reductionism denies this analogy. Two theoretical frameworks for these positions are introduced to better formulate the most popular version of persumptivism, a competence reliabilist account. Seven arguments against presumptivism are then stated and critiqued: (1) The argument from reliability; (2) The argument from reasons; (3) the argument from (...) positive reasons; (4) the argument from negative reasons; (5) the argument from agency; (6) the argument from psychological force; and (7) the argument from gullibility. If presumptivm is false, it is not for any of these arguments. (shrink)

The sceptic about the external world presents us with a paradox: an apparently acceptable argument for an apparently unacceptable conclusion—that we do not know anything about the external world. Some paradoxes, for instance the liar and the sorites, are very hard. The defense of a purported solution to either of these two inevitably deploys the latest in high-tech philosophical weaponry. On the other hand, some paradoxes are not at all hard, and may be resolved without much fuss. They do not (...) contain profound lessons about the human condition. Where should we place the sceptical paradoxes? (shrink)

According to evidentialists about inferential justification, an agent’s evidence—and only her evidence—determines which inferences she would be justified in making, whether or not she in fact makes them. But there seem to be cases in which two agents would be justified in making different inferences from a shared body of evidence, merely in virtue of the different competences those agents possess. These sorts of cases suggest that evidence does not have the pride of place afforded to it by evidentialists; competence (...) seems to play at least as important a role as evidence in explaining which inferences an agent would be justified in making. -/- In this paper, I consider how two versions of evidentialism about inferential justification might try to account for the role of competence in inference, and I present problems specific to each version. I end by sketching and briefly defending an alternative to these evidentialist views, “inferential dogmatism”. While dogmatic views have gotten some attention in debates around non-inferential justification, they have largely been ignored in debates around inferential justification and are to that extent novel. (shrink)

Forty years ago, Bayesian philosophers were just catching a new wave of technical innovation, ushering in an era of scoring rules, imprecise credences, and infinitesimal probabilities. Meanwhile, down the hall, Gettier’s 1963 paper [28] was shaping a literature with little obvious interest in the formal programs of Reichenbach, Hempel, and Carnap, or their successors like Jeffrey, Levi, Skyrms, van Fraassen, and Lewis. And how Bayesians might accommodate the discourses of full belief and knowledge was but a glimmer in the eye (...) of Isaac Levi. Forty years later, scoring rules, imprecise credences, and infinitesimal probabilities are all the rage. And the formal and “informal” traditions are increasingly coming together as Bayesian arguments spill over into debates about the foundations of empirical knowledge, skepticism, and more. Relatedly, Bayesian interest in full belief and knowledge has never been greater. Much more besides has happened in the last forty years of Bayesian philosophy, .. (shrink)

An introductory overview of the main issues in the epistemology of perception.