Eventually, Kuhlmann proposes a dispositional trope ontology, according to which particularized properties and not things are the most basic entities.

Quantum Field Theory (QFT) is the mathematical and conceptual framework for contemporary elementary particle physics. In a rather informal sense QFT is the extension of quantum mechanics (QM), dealing with particles, over to fields, i.e. systems with an infinite number of degrees of freedom. (See the entry on quantum mechanics.) In the last few years QFT has become a more widely discussed topic in philosophy of science, with questions ranging from methodology and semantics to ontology. QFT taken seriously in its (...) metaphysical implications seems to give a picture of the world which is at variance with central classical conceptions of particles and fields, and even with some features of QM. -/- The following sketches how QFT describes fundamental physics and what the status of QFT is among other theories of physics. Since there is a strong emphasis on those aspects of the theory that are particularly important for interpretive inquiries, it does not replace an introduction to QFT as such. One main group of target readers are philosophers who want to get a first impression of some issues that may be of interest for their own work, another target group are physicists who are interested in a philosophical view upon QFT. (shrink)

Quantum field theory provides the framework for many fundamental theories in modern physics, and over the last few years there has been growing interest in its historical and philosophical foundations. This anthology on the foundations of QFT brings together 15 essays by well-known researchers in physics, the philosophy of physics, and analytic philosophy.Many of these essays were first presented as papers at the conference?Ontological Aspects of Quantum Field Theory?, held at the Zentrum fr interdisziplin„re Forschung, Bielefeld, Germany. The essays contain (...) cutting-edge work on ontological aspects of QFT, including: the role of measurement and experimental evidence, corpuscular versus field-theoretic interpretations of QFT, the interpretation of gauge symmetry, and localization.This book is ideally suited to anyone with an interest in the foundations of quantum physics, including physicists, philosophers and historians of physics, as well as general readers interested in philosophy or science. (shrink)

Advocates of the New Mechanicism in philosophy of science argue that scientific explanation often consists in describing mechanisms responsible for natural phenomena. Despite its successes, one might think that this approach does not square with the ontological strictures of quantum mechanics. New Mechanists suppose that mechanisms are composed of objects with definite properties, which are interconnected via local causal interactions. Quantum mechanics calls these suppositions into question. Since mechanisms are hierarchical it appears that even macroscopic mechanisms must supervene on a (...) set of “objects” that behave non-classically. In this paper we argue, in part by appeal to the theory of quantum decoherence, that the universal validity of quantum mechanics does not undermine neo-mechanistic ontological and explanatory claims as they occur within in classical domains. Additionally, we argue that by relaxation of certain classical assumptions, mechanistic explanatory strategies can sometimes be carried over into the quantum domain. (shrink)

Despite a strong sensitization to the corruption problem and a large body of interdisciplinary research, scientists have only rarely investigated which motivational, volitional, emotional, and cognitive components make decision makers in companies act corruptly. Thus, we examined how their interrelation leads to corruption by proposing an action model. We tested the model using a business simulation game with students as participants. Results of the PLS structural equation modeling showed that both an attitude and subjective norm favoring corruption led to a (...) desire to act corruptly. Given high perceived behavioral control, this desire was transformed into an intention that finally resulted in corrupt action. Components related to general private and professional goals did not allow for any prediction. Based on these results, we discuss preventative measures and methods for combating intra- and inter-organizational corruption. (shrink)

Large changes of financial market prices without exogenous causes deviate significantly from the Gaussian behavior of random variables. This indicates that financial markets should be treated as complex systems, for which nonlinear interactions of its subunits/agents are crucial. I focus on how the complex systems perspective impacts the notion of explanations in economics. The mechanistic model seems to fit the bill, but problems surface on closer scrutiny. One characteristic of complex systems is that their behavior is surprisingly independent from microscopic (...) details. Thus, mechanistic explanations in the microreductionist manner seem unavailable. Despite these conflicts, I defend a modified structural mechanistic approach. (shrink)

In recent debates mechanisms are often discussed in the context of ‘complex systems’ which are understood as having a complicated compositional structure. I want to draw the attention to another, radically different kind of complex system, in fact one that many scientists regard as the only genuine kind of complex system. Instead of being compositionally complex these systems rather exhibit highly non-trivial dynamical patterns on the basis of structurally simple arrangements of large numbers of non-linearly interacting constituents. The characteristic dynamical (...) patterns in what I call “dynamically complex systems” arise from the interaction of the system’s parts largely irrespective of many properties of these parts. Dynamically complex systems can exhibit surprising statistical characteristics, the robustness of which calls for an explanation in terms of underlying generating mechanisms. However, I want to argue, dynamically complex systems are not sufficiently covered by the available conceptions of mechanisms. I will explore how the notion of a mechanism has to be modified to accommodate this case. Moreover, I will show under which conditions the widespread, if not inflationary talk about mechanisms in complex systems stretches the notion of mechanisms beyond its reasonable limits and is no longer legitimate. (shrink)

Agent-based models derive the behavior of artificial socio-economic entities computationally from the actions of a large number of agents. One objection is that highly idealized ABMs fail to represent the real world in any reasonable sense. Another objection is that they at best show how observed patterns may have come about, because simulations are easy to produce and there is no evidence that this is really what happens. Moreover, different models may well yield the same result. I will rebut these (...) objections by focusing on an often neglected, but crucial function of ABMs. Building on Gelfert’s account of the exploratory uses of scientific models I show that, in the absence of an accepted underlying theory, successful ABMs lend inductive support to assumptions concerning certain structural feutures of the behavioral rules employed. One core step towards this goal is what I call multiple-model robustness analysis. (shrink)

The following conjecture is due to Shelah–Hasson: Any infinite strongly NIP field is either real closed, algebraically closed, or admits a non‐trivial definable henselian valuation, in the language of rings. We specialise this conjecture to ordered fields in the language of ordered rings, which leads towards a systematic study of the class of strongly NIP almost real closed fields. As a result, we obtain a complete characterisation of this class.

Dieses Buch liefert dem Leser eine aktuelle und fundierte Einführung in die Philosophie der Quantenphysik. Obwohl sich die Quantentheorie durch spektakuläre empirische Erfolge auszeichnet, wird bis heute kontrovers diskutiert, wie sie zu verstehen ist. In diesem Werk geben die Autoren einen Überblick über die zahlreichen philosophischen Herausforderungen: Verletzen Quantenobjekte das Prinzip der Kausalität? Sind gleichartige Teilchen ununterscheidbar und daher keine Individuen? Behalten Quantenobjekte in der zeitlichen Entwicklung ihre Identität? Wie verhält sich ein zusammengesetztes Quantensystem zu seinen Teilen? Diese Fragen werden (...) im Rahmen verschiedener Deutungsansätze der Quantentheorie diskutiert. Ein Ausblick in die Quantenfeldtheorie verschärft das Hauptproblem der Nichtlokalität. Philosophie der Quantenphysik richtet sich an Philosophen mit Interesse für Physik, macht Physiker mit den philosophischen Fragen ihres Faches vertraut und liefert Anregungen für den gymnasialen Physik-Unterricht. Das Buch schließt damit eine Lücke zwischen populären Einführungen und spezialisierten Monografien zur Philosophie der Quantenphysik. In der vorliegenden zweiten Auflage wurde das Kapitel zu Verschränkung und Nicht-Lokalität deutlich erweitert und jedes Kapitel mit Übungsaufgaben und Musterlösungen ergänzt. (shrink)

Philosophy of physics is a small but thriving research field situated at the intersection between the natural sciences and the humanities. However, what exactly distinguishes philosophy of physics from physics is rarely made explicit in much depth. We provide a detailed analysis in the form of eleven theses, delineating both the nature of the questions asked in philosophy of physics and the methodology with which they are addressed.

This book provides a thorough and up-to-date introduction to the philosophy of quantum physics. Although quantum theory is renowned for its spectacular empirical successes, controversial discussion about how it should be understood continue to rage today. In this volume, the authors provide an overview of its numerous philosophical challenges: Do quantum objects violate the principle of causality? Are particles of the same type indistinguishable and therefore not individual entities? Do quantum objects retain their identity over time? How does a compound (...) quantum system relate to its parts? These questions are answered here within different interpretational approaches to quantum theory. Finally, moving to Quantum Field Theory, we find that the problem of non-locality is exacerbated. Philosophy of quantum physics is aimed at philosophers with an interest in physics, while also serving to familiarize physicists with many of the essential philosophical questions of their subject. (shrink)

We study the algebraic implications of the non-independence property and variants thereof on infinite fields, motivated by the conjecture that all such fields which are neither real closed nor separably closed admit a henselian valuation. Our results mainly focus on Hahn fields and build up on Will Johnson’s “The canonical topology on dp-minimal fields” :1850007, 2018).

To investigate whether making performance predictions affects prospective memory processing, we asked one group of participants to predict their performance in a PM task embedded in an ongoing task and compared their performance with a control group that made no predictions. A third group gave not only PM predictions but also ongoing-task predictions. Exclusive PM predictions resulted in slower ongoing-task responding both in a nonfocal and in a focal PM task. Only in the nonfocal task was the additional slowing accompanied (...) by improved PM performance. Even in the nonfocal task, however, was the correlation between ongoing-task speed and PM performance reduced after predictions, suggesting that the slowing was not completely functional for PM. Prediction-induced changes could be avoided by asking participants to additionally predict their performance in the ongoing task. In sum, the present findings substantiate a role of metamemory for attention-allocation strategies of PM. (shrink)

Transcendental pragmatics is the attempt to make Kants transcendental philosophy philosophically defensible by means of a reconstruction in terms of semiotics and the theory of communication. The central theses of transcendental pragmatics are: philosophical final justification is possible. The claim of radical fallibilism: "all propositions are fallible, therefore final justification is impossible" is false. Both theses are defended against H. Keuths critique, recently published in this journal. Radical fallibilism, which admits the application of the principle of fallibility to itself entangles (...) itself pecisely for this reason in a whole raw of contradictions. Keuths objections rest upon a misunderstanding. His critique does not demonstrate the invalidity of reflexive final justification arguments because he misses the essential feature of such arguments namely that they are intended as strictly reflexive arguments. (shrink)

We explain how the field of logarithmic-exponential series constructed in 20 and 21 embeds as an exponential field in any field of exponential-logarithmic series constructed in 9, 6, and 13. On the other hand, we explain why no field of exponential-logarithmic series embeds in the field of logarithmic-exponential series. This clarifies why the two constructions are intrinsically different, in the sense that they produce non-isomorphic models of Thequation image; the elementary theory of the ordered field of real numbers, with the (...) exponential function and restricted analytic functions. (shrink)

In [F.-V. Kuhlmann, S. Kuhlmann, S. Shelah, Exponentiation in power series fields, Proc. Amer. Math. Soc. 125 3177–3183] it was shown that fields of generalized power series cannot admit an exponential function. In this paper, we construct fields of generalized power series with bounded support which admit an exponential. We give a natural definition of an exponential, which makes these fields into models of real exponentiation. The method allows us to construct for every κ regular uncountable cardinal, 2κ pairwise non-isomorphic (...) models of real exponentiation , but all isomorphic as ordered fields. Indeed, the 2κ exponentials constructed have pairwise distinct growth rates. This method relies on constructing lexicographic chains with many automorphisms. (shrink)

Financial theory is in trouble. Market crashes and high volatility are only too familiar to everyone, although the standard theories predict that they hardly ever occur. According to the well-known and (partly due to its simplicity) still widely used random-walk model, the probabilities for price changes of, say, stocks should result in a Gaussian distribution. However, experience tells us that large changes occur far more often than ‘allowed’ by a Gaussian distribution. New models are needed which lead to realistic probability (...) distributions. ‘Econophysicists’ are particularly active in this field by constructing microscopic models of financial markets on the basis of various ideas and tools from physics. But in which sense do these models contribute scientific explanations? In this paper I will investigate what and how one exemplary econophysics model explains. (shrink)

We give a valuation theoretic characterization for a real closed field to be recursively saturated. This builds on work in [9], where the authors gave such a characterization forκ-saturation, for a cardinal$\kappa \ge \aleph _0 $. Our result extends the characterization of Harnik and Ressayre [7] for a divisible ordered abelian group to be recursively saturated.

Neste artigo o autor procura mostrar por que o princípio de universalização de Habermas não pode ser fundamentado reflexivamente, como o autor da Teoria do agir comunicativo sugere, bem pode ser considerado como um princípio central de uma filosofia moral.

Definition of the problems: The physician-patient-relationship is influenced by economically driven decisions. This study explores the ethical consensus in explaining economical backgrounds of therapeutic and diagnostic interventions to patients, and the clinical practices of patient information.Method: A combination of questionnaire send to members of relevant health care organisations (n=132) and interviews with physicians working in different clinical resorts (n=15).Results and conclusion: In general there is a consensus in truth-telling about the economical background, however this ethical principle in many cases is (...) neglected. Whenever possible physicians try to translate economically driven decisions into medical terms. There is a broad disagreement and a wide range of individual ethical preferences regarding patient information, that can not be controlled by patients in any way. (shrink)

Given an ordered fieldK, we compute the natural valuation and skeleton of the ordered multiplicative group (K >0, ·, 1, <) in terms of those of the ordered additive group (K,+,0,<). We use this computation to provide necessary and sufficient conditions on the value groupv(K) and residue field $\bar K$ , for theL ∞ε-equivalence of the above mentioned groups. We then apply the results to exponential fields, and describev(K) in that case. Finally, ifK is countable or a power series field, (...) we derive necessary and sufficient conditions onv(K) and $\bar K$ forK to be exponential. In the countable case, we get a structure theorem forv(K). (shrink)

Prenatal genetic analysis complicates problems of decision-making during pregnancy. After a brief summary of the new situation the article resumes the argumentation within the German feminist and the German church debate. The author proposes some activities for churches and theological arguments to support women's reproductive rights as well as the ebryos' right to live.

Motivation: There is an ongoing search for definitive and reliable biomarkers to forecast or predict imminent seizure onset, but to date most research has been limited to EEG with sampling rates <1,000 Hz. High-frequency oscillations have gained acceptance as an indicator of epileptic tissue, but few have investigated the temporal properties of HFOs or their potential role as a predictor in seizure prediction. Here we evaluate time-varying trends in preictal HFO rates as a potential biomarker of seizure prediction.Methods: HFOs were (...) identified for all interictal and preictal periods with a validated automated detector in 27 patients who underwent intracranial EEG monitoring. We used LASSO logistic regression with several features of the HFO rate to distinguish preictal from interictal periods in each individual. We then tested these models with held-out data and evaluated their performance with the area-under-the-curve of their receiver-operating curve. Finally, we assessed the significance of these results using non-parametric statistical tests.Results: There was variability in the ability of HFOs to discern preictal from interictal states across our cohort. We identified a subset of 10 patients in whom the presence of the preictal state could be successfully predicted better than chance. For some of these individuals, average AUC in the held-out data reached higher than 0.80, which suggests that HFO rates can significantly differentiate preictal and interictal periods for certain patients.Significance: These findings show that temporal trends in HFO rate can predict the preictal state better than random chance in some individuals. Such promising results indicate that future prediction efforts would benefit from the inclusion of high-frequency information in their predictive models and technological architecture. (shrink)

Previous research on whether source memory is enhanced for emotionally valenced sources yielded inconclusive results. To identify potential boundary conditions, we tested whether encoding instructions that promote affective versus different types of non-affective item-source-processing foster versus hamper source-valence effects. In both experiments, we used neutral words as items superimposed on emotional (positive & negative) or neutral pictures as sources. Source pictures were selected based on valence and arousal ratings collected in a pre-study such that only valence varied across sources. Source (...) memory was measured via multinomial modelling. In Experiment 1, we applied an affective, item-focused orienting task (OT; i.e. word-pleasantness ratings) during item-source encoding and found enhanced source memory for emotionally valenced (positive & negative) compared to neutral sources. In Experiment 2, we systematically manipulated encoding instructions and again found enhanced source memory for emotionally valenced sources with an affective OT. No such effects occurred in the non-affective conditions, where participants were instructed to integrate item and source (item-source-fit judgments), to focus on the item (living-non-living judgments), or to encode the items only, respectively. With intentional item encoding, however, source memory was surprisingly better for positive than negative sources. We conclude that source-valence effects might unfold only under affective processing. (shrink)

Die folgende Chronologie legt den Fokus auf die Grundlagen und Deutungen der Quantenphysik, sie ist keine Geschichte der Quantenphysik im Ganzen, insbesondere finden die speziellen Entwicklungen der Quantenfeldtheorie und der sich daraus entwickelnden Teilchenphysik keine Berücksichtigung.

Dieses Buch liefert dem Leser eine aktuelle und fundierte Einführung in die Philosophie der Quantenphysik. Obwohl sich die Quantentheorie durch spektakuläre empirische Erfolge auszeichnet, wird bis heute kontrovers diskutiert, wie sie zu verstehen ist. In diesem Werk geben die Autoren einen Überblick über die zahlreichen philosophischen Herausforderungen: Verletzen Quantenobjekte das Prinzip der Kausalität? Sind gleichartige Teilchen ununterscheidbar und daher keine Individuen? Behalten Quantenobjekte in der zeitlichen Entwicklung ihre Identität? Wie verhält sich ein zusammengesetztes Quantensystem zu seinen Teilen? Diese Fragen werden (...) im Rahmen verschiedener Deutungsansätze der Quantentheorie diskutiert. Ein Ausblick in die Quantenfeldtheorie verschärft das Hauptproblem der Nichtlokalität. Philosophie der Quantenphysik richtet sich an Philosophiestudierende mit Interesse für Physik, macht Physikerinnen und Physiker mit den philosophischen Fragen ihres Faches vertraut und liefert Lehramtsstudierenden und Lehrern Anregungen für den gymnasialen Physik-Unterricht. Das Buch schließt damit eine Lücke zwischen populären Einführungen und spezialisierten Monografien zur Philosophie der Quantenphysik im deutschsprachigen Lehrbuchmarkt. In der vorliegenden zweiten Auflage wurde das Kapitel zu Verschränkung und Nicht-Lokalität deutlich erweitert und jedes Kapitel mit Übungsaufgaben und Musterlösungen ergänzt. cord friebezurzeit="" vertretung="" der="" professur="" für="" analytische="" philosophie="" an="" universität="" des="" saarlandes.p. (shrink)

We extend the characterization of extremal valued fields given in [2] to the missing case of valued fields of mixed characteristic with perfect residue field. This leads to a complete characterization of the tame valued fields that are extremal. The key to the proof is a model theoretic result about tame valued fields in mixed characteristic. Further, we prove that in an extremal valued field of finitep-degree, the images of all additive polynomials have the optimal approximation property. This fact can (...) be used to improve the axiom system that is suggested in [8] for the elementary theory of Laurent series fields over finite fields. Finally we give examples that demonstrate the problems we are facing when we try to characterize the extremal valued fields with imperfect residue fields. To this end, we describe several ways of constructing extremal valued fields; in particular, we show that in every ℵ1saturated valued field the valuation is a composition of extremal valuations of rank 1. (shrink)

We propose a new masking technique for masking word stimuli. Drawing on the phenomena of metacontrast and paracontrast, we alternately presented two prime displays of the same word with the background color in one display matching the font color in the other display and vice versa. The sequence of twenty alterations was sandwich-masked by structure masks. Using this masking technique, we conducted evaluative priming experiments with positive and negative target and prime words. Significant priming effects were found – for primes (...) and targets drawn from the same as well as from different word sets. Priming effects were independent of prime discrimination performance in direct tests and they were still significant after the sample was restricted to those participants who showed random responding in the direct test. (shrink)

In 1638, the Jesuit, poet, preacher, and historianJohannes Bisselius published the first volume of his seasonal poem Deliciae Veris, Pleasures of Spring. The subtly composed, stylistically unique cycle is presented here for the first time in a modern edition with a German translation and insightful commentary, including an introduction to each poem.".

Die philosophiegeschichtlichen, sprachphilosophischen, rationalitäts- und wissenschaftstheoretischen Versuche einer Transformation der Philosophie, der Karl-Otto Apels Lebenswerk gilt, bezeichnet Apel deshalb als »Transzendentalpragmatik«, weil sie ihren Einheitssinn in dem Gedanken finden, daß nichts außer der menschlichen Praxis des Argumentierens die kontexttranszendierende Gültigkeit unserer Meinungen über Tatsachen und Normen ermöglicht. Die einzelnen Beiträge beleuchten Konsequenzen und Probleme des transzendentalpragmatischen Programms in einem breiten Spektrum gegenwärtiger philosophischer Diskussionen, das von theoretischen Fragen der Bedeutungstheorie bis zu praktischen Fragen eines modernitätskritischen Dialogs zwischen »Erster« und »Dritter« (...) Welt reicht. (shrink)

Quantentheorie und Relativitätstheorie haben das Weltbild der Physik revolutioniert. Beide Theorien gelten jedoch als unanschaulich und schwer verständlich. Dieses Sachbuch schafft neue Zugänge und lädt zum Mitdenken ein. Renommierte Experten aus Physik und Philosophie erläutern Grundbegriffe, Erkenntnisfortschritte und Deutungsfragen zu Raum, Zeit und Materie. Dabei kommen typische Themen aus der Philosophie der Physik zur Sprache, wie etwa die Interpretationsdebatte der Quantentheorie oder Modellbildungen in der Kosmologie. Weltbildrelevante Fragen nach dem Verhältnis von Mathematik, Empirie und Anschauung oder nach der Verlässlichkeit physikalischer (...) Erkenntnis erfordern die Verbindung von Physik und Philosophie, von fachwissenschaftlicher Grundlagenforschung und methodenkritischer Reflexion. Der thematische Bogen geht zurück auf ein hochkarätig besetztes Symposium mit populärwissenschaftlicher Ausrichtung. Das Buch enthält Beiträge von Andreas Bartels, Robert Harlander, Paul Hoyningen-Huene, Gert-Ludwig Ingold, Claus Kiefer, Meinard Kuhlmann, Klaus Mainzer, Oliver Passon, Manfred Stöckler, Rüdiger Vaas und Reinhard Werner. (shrink)

In einem auf drei Bände angelegten Dokumentationswerk werden Entstehung und Ausbreitung des Paracelsismus in den kontroversen Verflechtungen der Wissenschafts-, Literatur- und Sozialgeschichte des späten 16. Jahrhunderts verankert. Die kritische Edition aufschlußreicher, oft in unbekanntes Terrain führender Texte ist begleitet von umfangreichen Kommentaren sowie von biographischen Darstellungen der Urheber, Adressaten, Gegner bzw. Sympathisanten der paracelsistischen Reform und Protestbewegung. Der zweite Band des »Corpus Paracelsisticum« erschließt das weitläufige Oeuvre von Michael Toxites und Gerhard Dorn, wirkmächtige Gründergestalten des oberrheinischen Paracelsismus. Von da aus (...) fällt der Blick quer über die Konfessionsgrenzen auf andere kulturelle Zentren in Bayern, Sachsen, Schlesien, Böhmen und am Niederrhein. Mit Verfassern wie G. Fedro, M. Ambrosius, L. Span, B. Flöter, G. Etschenreutter, B. Scultetus, P. Perna, Th. Zwinger und J. Albrecht eröffnet sich ein epochaler, äußerst weitläufiger Diskurszusammenhang. In ihm lassen sich doxographische, methodische, hermeneutische, sprachtheoretische und überlieferungsspezifische Auseinandersetzungen ebenso beobachten wie Tendenzen einer theosophischen Spiritualisierung und heterodoxen Aufladung der in Paracelsus' Namen entwickelten Anthropologie und Kosmologie. Direkte Verbindungen ergeben sich unter anderem zu führenden Vertretern der sogenannten Schwenckfelder, damit auch zu Fraktionen aktiver protestantischer Dissidenten. Der Band wird neben dem weiterführenden Kommentar begleitet von einer ausführlichen Einleitung und erschlossen nicht nur durch mehrere Register, sondern auch durch wissenschaftshistorische Zusammenfassungen zu jedem Autorcorpus. (shrink)

Der zweite Band des "Corpus Paracelsisticum" erschließt das weitläufige Oeuvre von Michael Toxites und Gerhard Dorn, wirkmächtige Gründergestalten des oberrheinischen Paracelsismus. Von da aus fällt der Blick quer über die Konfessionsgrenzen auf andere kulturelle Zentren in Bayern, Sachsen, Schlesien, Böhmen und am Niederrhein. Mit Verfassern wie G. Fedro, M. Ambrosius, L. Span, B. Flöter, G. Etschenreutter, B. Scultetus, P. Perna, Th. Zwinger und J. Albrecht eröffnet sich ein epochaler, äußerst weitläufiger Diskurszusammenhang. Der Band wird neben dem weiterführenden Kommentar begleitet von (...) einer ausführlichen Einleitung und erschlossen durch mehrere Register sowie wissenschaftshistorische Zusammenfassungen zu jedem Autorcorpus. (shrink)

Given a Henselian valuation, we study its definability (with and without parameters) by examining conditions on the value group. We show that any Henselian valuation whose value group is not closed in its divisible hull is definable in the language of rings, using one parameter. Thereby we strengthen known definability results. Moreover, we show that in this case, one parameter is optimal in the sense that one cannot obtain definability without parameters. To this end, we present a construction method for (...) a t-Henselian non-Henselian ordered field elementarily equivalent to a Henselian field with a specified value group. (shrink)