Adaptive Logics as a Necessary Tool for Relative Rationality: Including a Section on Logical Pluralism

In this paper, I show that adaptive logics are required by my epistemological stand. While doing so, I defy the reader to cope with the problems I am able to cope with. The last section of the paper contains a defense of a specific form of logical pluralism. Although this section is an integral part of the paper, it may be read separately

Bloody analogical reasoning

In this paper I will study some of William Harvey's applications of analogies in the Prelectiones Anatomiae Universalis and the Exercitatio anatomica de motu cordis et sanguinis in animalibus. I will show that Harvey applied analogies in many different ways and that some contributed to the discovery of the characteristic 'action' of the heart and pulse and even to the discovery of the blood circulation. The discovery process will be approached as a problem solving process as described in Batens' contextual model. The focus on constraints allows to see Harvey both as a modern because of his extensive use of experimental results and as strongly influenced by an Aristotelian 'natural philosophy interpretation' of anatomy and physiology as, for instance, propagated by Fabricius of Aquapendente

Avoiding deontic explosion by contextually restricting aggregation

In this paper, we present an adaptive logic for deontic conflicts, called P2.1(r), that is based on Goble's logic SDLaPe-a bimodal extension of Goble's logic P that invalidates aggregation for all prima facie obligations. The logic P2.1(r) has several advantages with respect to SDLaPe. For consistent sets of obligations it yields the same results as Standard Deontic Logic and for inconsistent sets of obligations, it validates aggregation "as much as possible". It thus leads to a richer consequence set than SDLaPe. The logic P2.1(r) avoids Goble's criticisms against other non-adjunctive systems of deontic logic. Moreover, it can handle all the 'toy examples' from the literature as well as more complex ones

A Boolean Extension of KLM-Style Conditional Reasoning

Propositional KLM-style defeasible reasoning involves extending propositional logic with a new logical connective that can express defeasible (or conditional) implications, with semantics given by ordered structures known as ranked interpretations. KLM-style defeasi- ble entailment is referred to as rational whenever the defeasible entail- ment relation under consideration generates a set of defeasible implica- tions all satisfying a set of rationality postulates known as the KLM postulates. In a recent paper Booth et al. proposed PTL, a logic that is more expressive than the core KLM logic. They proved an impossibility result, showing that defeasible entailment for PTL fails to satisfy a set of rationality postulates similar in spirit to the KLM postulates. Their interpretation of the impossibility result is that defeasible entailment for PTL need not be unique. In this paper we continue the line of research in which the expressivity of the core KLM logic is extended. We present the logic Boolean KLM (BKLM) in which we allow for disjunctions, conjunctions, and negations, but not nesting, of defeasible implications. Our contribution is twofold. Firstly, we show (perhaps surprisingly) that BKLM is more expressive than PTL. Our proof is based on the fact that BKLM can characterise all single ranked interpretations, whereas PTL cannot. Secondly, given that the PTL impossibility result also applies to BKLM, we adapt the different forms of PTL entailment proposed by Booth et al. to apply to BKLM

Dialetheism in Action: A New Strategy for Solving the Equal Validity Paradox

This paper starts from the Equal Validity Paradox, a paradoxical argument connected to the so-called phenomenon of faultless disagreement. It is argued that there are at least six strategies for solving the paradox. After presenting the first five strategies and their main problems, the paper focuses on the sixth strategy which rejects the assumption that every proposition cannot be both true a false. Dialetheism is the natural candidate for developing strategy six. After presenting strategy six in detail, we formulate a normative problem for the dialetheist and offer a tentative solution to it. We then elaborate further considerations connecting strategy six to pluralism about truth and logic. Even if strategy six is a hard path to take, its scrutiny highlights some important points on truth, logic and the norms for acceptance and rejection