I. Psychologism,Functionalism, and the modal status of logical Laws

In a recent article (Inquiry, Vol. 19 [1976]), J. W. Meiland addresses the issue of psychologism in logic, which holds that logic is a branch of psychology and that logical laws (such as the Principle of Non‐Contradiction) are contingent upon the nature of the mind. Meiland examines Husserl's critique of psychologism, argues that Husserl is not convincing, and offers two new objections to the psychologistic thesis. In this paper I attempt to rebut those objections. In question are the acceptable criteria for determining the possibility or impossibility of systems of logic significantly different from our own. I argue that a criteriological application of our accepted laws of logic to this question commits a circular fallacy. I then argue that, even if we accept logical consistency as a criterion for possibility, a plausible argument for the possibility of valid alternative logics can be constructed by using the functionalist analogy between minds and automata. Finally, I attempt to rebut the claim that in logic the only changes possible are conceptual changes that would not permit a proposition to be both true and false.     

Husserl and the Algebra of Logic: Husserl’s 1896 Lectures

In his 1896 lecture course on logic–reportedly a blueprint for the Prolegomena to Pure Logic–Husserl develops an explicit account of logic as an independent and purely theoretical discipline. According to Husserl, such a theory is needed for the foundations of logic (in a more general sense) to avoid psychologism in logic. The present paper shows that Husserl’s conception of logic (in a strict sense) belongs to the algebra of logic tradition. Husserl’s conception is modeled after arithmetic, and respectively logical inferences are viewed as analogical to arithmetical calculation. The paper ends with an examination of Husserl’s involvement with the key characters of the algebra of logic tradition. It is concluded that Ernst Schr?der, but presumably also Hermann and Robert Grassmann influenced Husserl most in his turn away from psychologism.     

Analysis versus laws boole’s explanatory psychologism versus his explanatory anti-psychologism

This paper discusses George Boole’s two distinct approaches to the explanatory relationship between logical and psychological theory. It is argued that, whereas in his first book he attributes a substantive role to psychology in the foundation of logical theory, in his second work he abandons that position in favour of a linguistically conceived foundation. The early Boole espoused a type of psychologism and later came to adopt a type of anti-psychologism. To appreciate this invites a far-reaching reassessment of his philosophy of logic     

What is it to Depsychologize Psychology?

In this essay, I distinguish two ways of depsychologizing psychology: ‘anti‐psychologism’ and ‘non‐psychologism’. Both positions are responses to the Fregean sharp distinction between the logical and the psychological. But where anti‐psychologism, which I find in John McDowell, attempts to overcome the sharp distinction by arguing that psychological states and their expressions are apt to be articulated into judgments, Stanley Cavell's non‐psychologism, a powerful and neglected alternative, wants to overcome the sharp distinction by abandoning judgment as the paradigm expression of thought and communication.     

The limits of conceivability: logical cognitivism and the language faculty

Robert Hanna (Rationality and logic. MIT Press, Cambridge, 2006) articulates and defends the thesis of logical cognitivism, the claim that human logical competence is grounded in a cognitive faculty (in Chomsky’s sense) that is not naturalistically explicable. This position is intended to steer us between the Scylla of logical Platonism and the Charybdis of logical naturalism (/psychologism). The paper argues that Hanna’s interpretation of Chomsky is mistaken. Read aright, Chomsky’s position offers a defensible version of naturalism, one Hanna may accept as far as his version of naturalism goes, although not one that supports the claim that cognitive science offers a place for logic that is somehow outside the natural, contingent order.     

Reply to Dr. Lambert

Psychologism in logic holds that logic is a branch of psychology. This view has been vigorously defended by John Stuart Mill and by a number of German philosophers of logic, notably Erdmann. Its chief critics have been Husserl and Frege and, to a lesser extent, Russell. Husserl set forth a profound and detailed critique of psychologism in Logical Investigations. This paper examines this critique. First, I explain why the psychologistic theory is attractive. Then I show that Husserl's critique is not convincing, partly because he does not take the theory in its most plausible form and partly because he ignores certain important distinctions (for example, between what a statement is about and what it is true in virtue of). Then I raise two new objections to the psychologistic theory. The purpose of this paper is to suggest that the psychologistic theory remains an important and serious position from which we can learn much about the status of logic.     

The long way to “extreme psychologism”

In “Clearing Space for Extreme Psychologism about Reasons”, Mitova argues against two main views about the ontology of reasons. Instead, she presents an argument by elimination for “extreme psychologism” as a prima facie superior alternative. I will argue for the following claims. First, the case against the Standard Story – the view that normative and motivating reasons are facts and psychological states, respectively – includes premises that are in need of support. Second, the critical examination of factualism – the view that normative and motivating reasons are facts – misses a relevant distinction between motivating and explanatory reasons. This distinction brings new resources to factualism to answer the raised worries. Third, the case for extreme psychologism rests on a requirement that is either too easy to threaten other alternatives, or so strong as to challenge extreme psychologism itself.     

The force and the content of judgment

This essay explores what it means to reject Frege's distinction of force and content: the rejection completes Frege's anti‐psychologism as it leaves no space for a psychological concept of judgment distinct from the logical concept, which is the concern of no empirical science, but of logic. It emerges that logic, as the science of judgement, is — not a metaphysics of judgement, but — metaphysics. And it emerges that the opposition of subject to subject — the elementary nexus of thinker to thinker in dialogue — is contained within the logical concept of judgment.     

On the Proximity of the Logical and ‘Objective Bayesian’ Interpretations of Probability

In his Bayesian Nets and Causality, Jon Williamson presents an ‘Objective Bayesian’ interpretation of probability, which he endeavours to distance from the logical interpretation yet associate with the subjective interpretation. In doing so, he suggests that the logical interpretation suffers from severe epistemological problems that do not affect his alternative. In this paper, I present a challenge to his analysis. First, I closely examine the relationship between the logical and ‘Objective Bayesian’ views, and show how, and why, they are highly similar. Second, I argue that the logical interpretation is not manifestly inferior, at least for the reasons that Williamson offers. I suggest that the key difference between the logical and ‘Objective Bayesian’ views is in the domain of the philosophy of logic; and that the genuine disagreement appears to be over Platonism versus nominalism (within weak psychologism).

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Psychologism Revisited in Logic, Metaphysics, and Epistemology

Psychologism is a philosophical ideology that seeks to explain the principles of logic, metaphysics, and epistemology as psychological phenomena. Psychologism has been the storm center of concerted criticisms since the nineteenth century, and is thought by many to have been refuted once and for all by Kant, Frege, Husserl, and others. The project of accounting for objective philosophical or mathematical truths in terms of subjective psychological states has been largely discredited in mainstream analytic thought. Ironically, psychologism has resurfaced in unexpected guises in the form of intuitionistic logic and mathematics, cognitivism, and naturalized epistemology. I examine some of the principal objections to psychologism – distinguishing roughly between good and bad or philosophically acceptable versus unacceptable psychologism – and consider the extent to which a new wave of psychologism may be gaining prominence in contemporary philosophy, and the light its successes and failures may shed on the original concept and underlying perspective of classical psychologism.     

Thomason’s Paradox for Belief,and Two Consequence Relations

Thomason (1979/2010)’s argument against competence psychologism in semantics envisages a representation of a subject’s competence as follows: he understands his own language in the sense that he can identify the semantic content of each of its sentences, which requires that the relation between expression and content be recursive. Then if the scientist constructs a theory that is meant to represent the body of the subject’s beliefs, construed as assent to the content of the pertinent sentences, and that theory satisfies certain ‘natural assumptions’, then it implies that the subject is inconsistent if the beliefs include arithmetic. I challenge the result by insisting that the motivation for Thomason’s principle (ii), via Moore’s Paradox, leads to a more complex representation, in which stating the facts and expressing one’s beliefs are treated differently. Certain logical connections among expressions of assent, and between expression and statement, are a matter of consequence on pain of pragmatic incoherence, not consequence on pain of classical logical inconsistency. But while this salvages the possibility that a modification of the above sort of representation could be adequate, Thomason’s devastating conclusion returns if the scientist identifies himself as the subject of that representation, even when paying heed to the requirement of pragmatic coherence of the sort highlighted by Moore’s Paradox.     

Psychologism as a style of reasoning and the study of persons

“Psychologism” is proposed as a “style of reasoning” dominant in psychology that has set the agenda for determining what counts as psychological phenomena, their nature, and how they are to be investigated and understood. The assumptions of psychologism and particularities of its procedure are detailed and, subsequently, illustrated by example using the psychological study of attitudes. The failure of psychologism is raised and an alternative to the conception of persons implicit in psychologism is discussed as an initial step in forging a style of reasoning adequate to psychological inquiry.     

Wie Natürlich ist das System der Natürlichen Deduktion?

How natural is natural deduction?– Gentzen's system of natural deduction intends to fit logical rules to the effective mathematical reasoning in order to overcome the artificiality of deductions in axiomatic systems (¶ 2). In spite of this reform some of Gentzen's rules for natural deduction are criticised by psychologists and natural language philosophers for remaining unnatural. The criticism focuses on the principle of extensionality and on formalism of logic (¶ 3). After sketching the criticism relatively to the main rules, I argue that the criteria of economy, simplicity, pertinence etc., on which the objections are based, transcend the strict domain of logic and apply to arguments in general (¶ 4). (¶ 5) deals with Frege's critique of the concept of naturalness as regards logic. It is shown that this concept means a regression into psychologism and is exposed to the same difficulties as are: relativity, lack of precision, the error of arguing from `is' to `ought' (the naturalistic fallacy). Despite of these, the concept of naturalness plays the role of a diffuse ideal which favours the construction of alternative deductive systems in contrast to the platonic conception of logic (¶ 6).     

Gottlob Frege und Rudolf Eucken—Gesprächspartner in der Herausbildungsphase der modernen Logik

Frege and Eucken were colleagues in the faculty of philosophy at Jena University for more than 40 years. At times they had close scientific contacts. Eucken promoted Frege's career at the university. A comparison of Eucken's writings between 1878 and 1880 with Frege's writings shows Eucken to have had an important philosophical influence on Frege's philosophical development between 1879 and 1885. In particular the classification of the Begriffsschrift in the tradition of Leibniz is influenced by Eucken. Eucken also influenced Frege's choice of philosophical and logical terms. Finally, there are analogous positions concerning relations between concepts and their expressions in natural language, Frege was probably also influenced by Eucken's use of the term ‘tone’. Eucken used Frege's arguments in his own fight against psychologism and empiricism.     

No Future

The difficulties with formalizing the intensional notions necessity, knowability and omniscience, and rational belief are well-known. If these notions are formalized as predicates applying to (codes of) sentences, then from apparently weak and uncontroversial logical principles governing these notions, outright contradictions can be derived. Tense logic is one of the best understood and most extensively developed branches of intensional logic. In tense logic, the temporal notions future and past are formalized as sentential operators rather than as predicates. The question therefore arises whether the notions that are investigated in tense logic can be consistently formalized as predicates. In this paper it is shown that the answer to this question is negative. The logical treatment of the notions of future and past as predicates gives rise to paradoxes due the specific interplay between both notions. For this reason, the tense paradoxes that will be presented are not identical to the paradoxes referred to above.     

Deviance and Vice: Strength as a Theoretical Virtue in the Epistemology of Logic

This paper is about the putative theoretical virtue of strength, as it might be used in abductive arguments to the correct logic in the epistemology of logic. It argues for three theses. The first is that the well‐defined property of logical strength is neither a virtue nor a vice, so that logically weaker theories are not—all other things being equal—worse or better theories than logically stronger ones. The second thesis is that logical strength does not entail the looser characteristic of scientific strength, and the third is that many modern logics are on a par—or can be made to be on a par—with respect to scientific strength.     

Logical pluralism without the normativity

Logical pluralism is the view that there is more than one logic. Logical normativism is the view that logic is normative. These positions have often been assumed to go hand-in-hand, but we show that one can be a logical pluralist without being a logical normativist. We begin by arguing directly against logical normativism. Then we reformulate one popular version of pluralism—due to Beall and Restall—to avoid a normativist commitment. We give three non-normativist pluralist views, the most promising of which depends not on logic’s normativity but on epistemic goals.