Bolzano on Necessary ExistenceArchiv für Geschichte der Philosophie


Stefan Roski, Paul Rusnock


Anomalous coronary vessels

On Topaz

On Ideas

Bernard Bolzano, Jan Berg, Burnham Terrell

Der Humanist Bernard Bolzano



DOI 10.1515/agph-2014-0015   AGPh 2014; 96(3): 320–359

Stefan Roski and Paul Rusnock

Bolzano on Necessary Existence

Abstract: This paper is devoted to an examination of Bolzano’s notion of necessary existence, which has so far received relatively little attention in the literature. We situate Bolzano’s ideas in their historical context and show how he proposed to correct various flaws of his predecessors’ definitions. Further, we relate

Bolzano’s conception to his metaphysical and theological assumptions, arguing that some consequences of his definition which have been deemed counterintuitive by some of his interpreters turn out to be more reasonable given the broadly

Leibnizian background of his metaphysics. Finally, we consider some difficulties that arise from Bolzano’s evolving views on freedom, which, at least in his early thought, was intimately linked with contingency. In an appendix, we discuss a recent debate on Bolzano’s notion of necessary truth between Textor and Rusnock that has some bearing on our overall line of interpretation of Bolzano’s notion of necessary existence.

Stefan Roski: Philosophisches Seminar, Universität Hamburg, Von Melle-Park 6, 20146 Hamburg;

Paul Rusnock: Department of Philosophy, University of Ottawa, 55 Laurier Avenue East, Ottawa,

Ontario, Canada K1N 6N5; 1 Introduction

Modal notions play a central role in metaphysics, and Bolzano accordingly places great importance on arriving at correct definitions of them:

Statements of necessity, possibility and contingency […] are on everyone’s lips, and the most important investigations on God, freedom, etc., depend on a correct determination of these concepts.¹

Yet his definitions of necessity and related notions in terms of purely conceptual truth have caused a great deal of perplexity for modern readers, who have found them unmotivated, obviously too broad, and just plain strange. 1 Bolzano 1841, 61.

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Bolzano on Necessary Existence   321

In this essay, we attempt to shed some light on his views on necessity in the proper sense, namely, necessary existence. Our approach is purely historical. We do not seek to defend Bolzano’s account, which is based in large part on metaphysical theses that, although popular in the eighteenth and early nineteenth centuries, will find few if any adherents today. Rather, by considering his work in its historical context, we aim to explain his position, and to show that features, which can appear odd from a contemporary perspective, are defensible and perhaps even reasonable given his assumptions.

The most extensive previous discussion of Bolzano’s concept of necessary existence may be found in Mark Textor’s thorough and enlightening study Bolzano’s Propositionalismus.² Textor has argued that, despite Bolzano’s insistence that his aim was to characterize necessity objectively,³ his definition must be understood in subjective terms, namely, in terms of the concepts that humans can form.

Otherwise, he argues, Bolzano would be forced to admit that every actual object exists necessarily.⁴ Independently of this problem, Textor has criticized Bolzano’s definition as too broad. He has pointed out that many objects which exist necessarily according to the definition clearly do not exist in every metaphysically possible world. Assuming that Bolzano’s definition is supposed to capture the notion of metaphysically necessary existence, Textor concluded that Bolzano’s account is inadequate.⁵

In our essay, we offer a different interpretation. We show that Textor’s argument in support of the claim that Bolzano’s definition has to be read subjectively is not compelling. Further, we will answer his second objection by clarifying the motivation behind Bolzano’s definition against the background of his metaphysico-theological views. Following the general thrust of Rusnock’s recent interpretation of Bolzano’s views on necessary truth,⁶ we argue that his aim was to capture a notion of necessary existence that is broad enough to capture both metaphysically and morally necessary existence in Leibniz’s sense. That is to say, Bolzano tried to capture a notion according to which all objects that God had to create because of his perfect goodness also exist necessarily. Contrary to Leibniz, however, Bolzano did not believe that this class comprises all actually existing objects. A striking feature of Bolzano’s conception that, we argue, becomes understandable against this background is that there are necessary totalities whose parts are contingent. 2 Textor 1996. 3 Cf. Bolzano 1839, 143. 4 Textor 1996, 296 f. 5 Textor 1996, 336. 6 Rusnock 2012.

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The structure of our essay will be as follows. After a preliminary discussion of some Bolzanian notions that are needed to understand his definition (Section 2), we present the definition in Section 3, describing how Bolzano may have arrived at it by considering technical problems he saw with definitions given by his predecessors. We then consider the scope of his intentions in framing his definition. In Section 4, we turn to the application of his definition. Here, we examine

Bolzano’s arguments for the existence of contingent entities, Textor’s arguments in favor of a subjective interpretation, and the question of necessary totalities.

In Section 5, finally, we point out a problem with Bolzano’s position that results from his evolving views on freedom, which, at least in his early thought, he took to be intimately linked with contingency. There follows an appendix commenting on the recent discussion of Bolzano’s notion of necessary truth in articles by

Rusnock and Textor. 2 Preliminaries: Bolzano’s Fundamental Notions