BackgroundPreprint usage is growing rapidly in the life sciences; however, questions remain on the relative quality of preprints when compared to published articles. An objective dimension of quality that is readily measurable is completeness of reporting, as transparency can improve the reader’s ability to independently interpret data and reproduce findings.MethodsIn this observational study, we initially compared independent samples of articles published in bioRxiv and in PubMed-indexed journals in 2016 using a quality of reporting questionnaire. After that, we performed paired comparisons (...) between preprints from bioRxiv to their own peer-reviewed versions in journals.ResultsPeer-reviewed articles had, on average, higher quality of reporting than preprints, although the difference was small, with absolute differences of 5.0% [95% CI 1.4, 8.6] and 4.7% [95% CI 2.4, 7.0] of reported items in the independent samples and paired sample comparison, respectively. There were larger differences favoring peer-reviewed articles in subjective ratings of how clearly titles and abstracts presented the main findings and how easy it was to locate relevant reporting information. Changes in reporting from preprints to peer-reviewed versions did not correlate with the impact factor of the publication venue or with the time lag from bioRxiv to journal publication.ConclusionsOur results suggest that, on average, publication in a peer-reviewed journal is associated with improvement in quality of reporting. They also show that quality of reporting in preprints in the life sciences is within a similar range as that of peer-reviewed articles, albeit slightly lower on average, supporting the idea that preprints should be considered valid scientific contributions. (shrink)

Na obra Eichmann em Jerusalém – um relato sobre a banalidade do mal, Hannah Arendt descreve em determinada passagem que o réu Otto Adolf Eichmann invoca o imperativo categórico de Immanuel Kant, na busca de justificar sua conduta criminosa no massacre ocorrido na Alemanha nazista. Inertes numa sociedade desfigurada e que apresentava novas leis, tanto o réu quanto os demais criminosos viviam sob um véu de cegueira, que não poderia, porém, ser fundamento para a barbaridade cometida. Pretende-se com esse artigo (...) elucidar o imperativo categórico de Kant empregado na ótica das leis da razão e, analisar o mau uso da autoridade de Kant por Eichmann. (shrink)

Over recent years, the research community has been increasingly using preprint servers to share manuscripts that are not yet peer-reviewed. Even if it enables quick dissemination of research findings, this practice raises several challenges in publication ethics and integrity. In particular, preprints have become an important source of information for stakeholders interested in COVID19 research developments, including traditional media, social media, and policy makers. Despite caveats about their nature, many users can still confuse pre-prints with peer-reviewed manuscripts. If unconfirmed but (...) already widely shared first-draft results later prove wrong or misinterpreted, it can be very difficult to “unlearn” what we thought was true. Complexity further increases if unconfirmed findings have been used to inform guidelines. To help achieve a balance between early access to research findings and its negative consequences, we formulated five recommendations: (a) consensus should be sought on a term clearer than ‘pre-print’, such as ‘Unrefereed manuscript’, “Manuscript awaiting peer review” or ‘’Non-reviewed manuscript”; (b) Caveats about unrefereed manuscripts should be prominent on their first page, and each page should include a red watermark stating ‘Caution—Not Peer Reviewed’; (c) pre-print authors should certify that their manuscript will be submitted to a peer-review journal, and should regularly update the manuscript status; (d) high level consultations should be convened, to formulate clear principles and policies for the publication and dissemination of non-peer reviewed research results; (e) in the longer term, an international initiative to certify servers that comply with good practices could be envisaged. (shrink)

A obra Hacking e dispositivos tecnológicos nos faz compreender que um computador não é somente uma máquina que corresponde aos cliques do mouse, mas uma realidade técnica que permite estar em contato com o universo inteiro. Essa realidade tem na internet um instrumento poderoso dotado de algoritmos por meio dos quais é possível conduzir nossas condutas por um universo grandioso no qual aprendemos a participar de grupos, a sorrir, a odiar, a amar, a trabalhar, comer, acordar, dormir, entre outros. Contudo, (...) é importante nos precavermos contra a tecnofobia, ou sentir que a internet é uma encarnação do mal. Não é isso, a internet abre espaços para ter bons encontros, conhecer os mais variados objetos técnicos e construir uma aprendizagem por meio da experimentação. (shrink)

El presente artículo tiene como propósito exponer la implementación y evaluación de un modelo de intervención grupal para personas con consumo problemático de drogas, el cual tiene como teoría de base la Biología de la Cognición y del Amar de Humberto Maturana. Hipotetizamos que mediante laimplementación de este modelo de terapia grupal disminuyen los niveles de depresión y ansiedad en las personas con consumo problemático de drogas. Es una investigación cuasi experimental pre-post con grupo de control, donde se exponen los (...) resultados de la muestra del Grupo Tratamiento, perteneciente a la Comunidad Terapéutica Padre Alberto Hurtado de Arica y del Grupo Control, el cual corresponde a la Comunidad Terapéutica La Tirana de AltoHospicio. Los resultados obtenidos muestran las diferencias significativas entre ambos grupos.The present article has as purpose to expose the implementation and evaluation of a model of group intervention for people with problematic consumption of drugs, which has as base theory the Biology of Cognition and of Love of Humberto Maturana; hypothesizing diminish the depression levels and anxiety in people with problematic consumption of drugs by means of thismodel’s of group therapy implementation. It is an quasi experimental research pre-post with control group, where the results of the sample of two Group Treatment are exposed, one belonging to the Therapeutic Community Padre Alberto Hurtado of Arica and the Group Control, which corresponds to the Therapeutic Community La Tirana at Alto Hospicio. The obtained results show significant differences between both groups. (shrink)

En Libertad. Un panfleto civil, Carlos Pereda reconstruye una disyuntiva central en relación con las posibles interpretaciones del valor sobredeterminado de la libertad: o la libertad se entiende como autenticidad o se asume como autonomía. El modelo más simple de la primera alternativa postula una estructura jerárquica de deseos y habitualmente se lo vincula con la obra temprana de Harry Frankfurt. En el análisis que sigue, trataré de mostrar que la introducción de la noción de amor en la perspectiva (...) frankfurtiana permite considerarla una versión que supera la disyuntiva entre autonomía y autenticidad al avanzar por un tercer camino: la idea de libertad como autorrealización, es decir, como la puesta en práctica de la capacidad de amar que permite a las personas bosquejar y perseguir ciertos fines últimos. (shrink)

Investigates the resolution of contradictions and ambiguous derogations in a code, by means of the imposition of partial orderings.

This article reports the findings of a survey examining if there are gender and career stage differences between male and female practitioners regarding ethical judgment. The results show that, on average, females adopted a more strict ethical stance than their male counterparts on 7 out of 19 vignettes. Males on the other hand, demonstrated a more ethical stance than their female counterparts on 2 out of 19 vignettes. The results furthermore indicate there is a significant difference in ethical judgment across (...) career stages. Overall, it appears that practitioners in later career stages display higher ethical judgment than practitoners in lower career stages. Implications are provided for both practitioners and academicians. (shrink)

This paper explores aspects of GPT-3 that have been discussed as harbingers of artificial general intelligence and, in particular, linguistic intelligence. After introducing key features of GPT-3 and assessing its performance in the light of the conversational standards set by Alan Turing in his seminal paper from 1950, the paper elucidates the difference between clever automation and genuine linguistic intelligence. A central theme of this discussion on genuine conversational intelligence is that members of a linguistic community never merely respond “algorithmically” (...) to queries through a selective kind of pattern recognition, because they must also jointly attend and act with other speakers in order to count as genuinely intelligent and trustworthy. This presents a challenge for systems like GPT-3, because representing the world in a way that makes conversational common ground salient is an essentially collective task that we can only achieve jointly with other speakers. Thus, the main difficulty for any artificially intelligent model of conversation is to account for the communicational intentions and motivations of a speaker through joint attention. These joint motivations and intentions seem to be completely absent from the standard way in which systems like GPT-3 and other artificial intelligent systems work. This is not merely a theoretical issue. Since GPT-3 and future iterations of similar systems will likely be available for commercial use through application programming interfaces, caution is needed regarding the risks created by these systems, which pass for “intelligent” but have no genuine communicational intentions, and can thereby produce fake and unreliable linguistic exchanges. (shrink)

What are the limits of the use of artificial intelligence (AI) in the relational aspects of medical and nursing care? There has been a lot of recent work and applications showing the promise and efficiency of AI in clinical medicine, both at the research and treatment levels. Many of the obstacles discussed in the literature are technical in character, regarding how to improve and optimize current practices in clinical medicine and also how to develop better data bases for optimal parameter (...) adjustments and predictive algorithms. This paper argues that there are also in principle obstacles to the application of AI in clinical medicine and care where empathy is important, and that these problems cannot be solved with any of the technical and theoretical approaches that shape the current application of AI in specific areas of clinical medicine in which care for patients is fundamental. This is important, because it generates specific risks that may be overlooked otherwise, and it justifies the necessity of human monitoring and emotional intervention in clinical medicine. Consequently, difficult issues concerning moral and legal responsibility may ensue if these in principle problems are ignored. (shrink)

Recent work in the philosophy of biology has attempted to clarify and defend the use of the biodiversity concept in conservation science. I argue against these views, and give reasons to think that the biodiversity concept is a poor fit for the role we want it to play in conservation biology on both empirical and conceptual grounds. Against pluralists, who hold that biodiversity consists of distinct but correlated properties of natural systems, I argue that the supposed correlations between these properties (...) are not tight enough to warrant treating and measuring them as a bundle. I additionally argue that deflationary theories of biodiversity don’t go far enough, since a large proportion of what we value in the environment falls outside bounds of what could reasonably be called “diversity”. I suggest that in current scientific practice biodiversity is generally an unnecessary placeholder for biological value of all sorts, and that we are better off eliminating it from conservation biology, or at least drastically reducing its role. (shrink)

The Polish logician Roman Suszko has extensively pleaded in the 1970s for a restatement of the notion of many-valuedness. According to him, as he would often repeat, “there are but two logical values, true and false.” As a matter of fact, a result by W´ojcicki-Lindenbaum shows that any tarskian logic has a many-valued semantics, and results by Suszko-da Costa-Scott show that any many-valued semantics can be reduced to a two-valued one. So, why should one even consider using logics with more (...) than two values? Because, we argue, one has to decide how to deal with bivalence and settle down the tradeoff between logical 2-valuedness and truth-functionality, from a pragmatical standpoint. -/- This paper will illustrate the ups and downs of a two-valued reduction of logic. Suszko’s reductive result is quite non-constructive.We will exhibit here a way of effectively constructing the two-valued semantics of any logic that has a truth-functional finite-valued semantics and a sufficiently expressive language. From there, as we will indicate, one can easily go on to provide those logics with adequate canonical systems of sequents or tableaux. The algorithmic methods developed here can be generalized so as to apply to many non-finitely valued logics as well —or at least to those that admit of computable quasi tabular two-valued semantics, the so-called dyadic semantics. (shrink)

This article presents what I call the Central Normative Proposal of Luis Villoro. This proposal is based on an interpretation of the principle of non-exclusion in ethics and epistemology. The core argument of the paper is based on a linguistic analogy that demonstrates the importance of reasonable communication for non-exclusion in epistemology, which is assumed in various theses of Villoro. A consequence of this analogy for non-exclusion in ethics is that Villoro defends basing what is reasonable on the concrete possibilities (...) of mutual understanding, starting with asymmetries and injustices that are obfuscated or eliminated in a contractualist analysis, or one that begins with strictly egalitarian principles. This criticism is compatible with egalitarian views, but it assumes a radically different point of departure. Although various theses by Villoro are compatible with egalitarian notions, given this point of departure based on asymmetries of power his proposal should be understood based on our cognitive capacities to understand and appreciate such asymmetries. For this reason, the paper concludes with an analysis of the notion of reasonableness, which under my interpretation Villoro defines in terms of our capacities for attention, that are not reducible to beliefs or systems of beliefs. In this way, the Central Normative Proposal of Villoro depends on the convergence between truth and the dignity of the members of communities in which as matter-of-fact asymmetries exist and must be eliminated through concrete communicative efforts. (shrink)

The present text surveys and reevaluates the meaning and scope of Ortega y Gasset’s philosophy. The chapters reveal the most important aspects of his history such as the Neokantian training he went thru in Germany as well as his discovery of Husserl’s phenomenology around 1912. The work also covers his original contributions to philosophy namely vital and historical reason - and the cultural and educational mission he proposed to achieve. The Spanish – and to a certain extent the European – (...) circumstance was the milieu from which his work emerged but this does not limit Ortega’s scope. Rather, he believed that universal truths can only emerge from the particulars in which they are embedded. The publication in 2010 of a critical edition of his Complete Works opened worldwide access for many unpublished manuscripts, and some of his lectures. There is renewed interest among students and researchers in Ortega and this book uniquely delivers scholarship on his content in English. (shrink)

Freire is one of the most powerful voices challenging the hegemony of bureaucratic and banking educational systems. His voice was particularly influential impacting revolutionary processes and progressive social movements while at the same time learning from their practices. However, some silences in his oeuvres requires further examination. In this article, we focus on the silences of Freire regarding education and its relationship with work and labor, gender issues, and citizenship building.

Many experts have warned that environmental degradation is increasing the likelihood of future pandemics like COVID-19, as habitat loss and poaching increase close contact between wildlife and people. This fact has been framed as a reason to increase wildlife conservation efforts. We have many good reasons to step up conservation efforts, but arguments for doing so on the basis of pandemic prevention are rhetorically, ethically, and empricially flawed.

This commentary focuses on the importance of attention skills in the development of universal associative learning, and it explains why the centrality of attention in UAL presents a considerable difficulty for the UAL approach. Attentional abilities are not just developmentally related to UAL but are in fact explanatory of UAL. The main problem is that all the types of attention involved in UAL can be dissociated from consciousness. This means that while attention skills for UAL might be necessary for consciousness, (...) they are not sufficient because they can all occur unconsciously. Thus, the possibility that UAL capacities might not be sufficient for consciousness cannot be eliminated, thereby challenging the key claim of the UAL approach. (shrink)

Mineral species are, at first glance, an excellent candidate for an ideal set of natural kinds somewhere beyond the periodic table. Mineralogists have a detailed set of rules and formal procedure for ratifying new species, and minerals are a less messy subject matter than biological species, psychological disorders, or even chemicals more broadly—all areas of taxonomy where the status of species as natural kinds has been disputed. After explaining how philosophers have tended to get mineralogy wrong in discussions of natural (...) kinds, I show how minerals species don’t behave like natural kinds. They are defined on the basis of human intentionality, not merely natural distinctions. They aren’t ideal grounds for inductive inference. And they don’t form a system that divides nature along a set of equivalent joints. While this is a regrettable outcome to those of us who like the idea of science relying on natural kinds, I contend that mineralogy is doing just fine without a natural kind-based taxonomy, and may in fact be better off without one. (shrink)

The objective of the present review on the evolution of Green Chemistry, since its emergence until 2016, aimed an integrated vision of its progress along the three phases of its development: emergence, divulgation and consolidation. The methodology involved the analysis of a selection of bibliography on the evolution of GC collected from issues of the ACS symposia series; editorials in specialized GC journals; and commemorative birthday papers/editorials of these journals and of the GC itself. The analysis allowed to identify and (...) discuss the characteristics and conceptions of GC agents about fundamental concepts and procedures, in order to visualize and better understand the state of knowledge and the subject areas that make up the field. The main alterations identified in the evolution of GC were: it acquired a better defined identity, with more participation of academy and increased scope; was progressively framed in sustainability; has been aspiring to a holistic frame and to a change on the nature of the innovation for its implementation, from incremental to transformative. The analysis suggests that for supporting expansion and consolidation of GC the following aspects deserve attention: full validation of chemical greenness by metrics; better characterization of the frontiers of GC research areas/themes; increased integration between academy and industry; and penetration in chemistry curricula. Its basic philosophy being the practice of a chemistry more focused on the environment preservation, GC means a new stage in nature and in the history of Chemistry. (shrink)

Supposedly, stubbornness on the part of scientists—an unwillingness to change one’s position on a scientific issue even in the face of countervailing evidence—helps efficiently divide scientific labor. Maintaining disagreement is important because it keeps scientists pursuing a diversity of leads rather than all working on the most promising, and stubbornness helps preserve this disagreement. Planck’s observation that “Science progresses one funeral at a time” might therefore be an insight into epistemically beneficial stubbornness on the part of researchers. In conversation with (...) extant formal models, recent empirical research, and a novel agent-based model of my own I explore whether the epistemic goods which stubbornness can secure—disagreement and diversity—are attainable through less-costly methods. I make the case that they are, at least in part, and also use my modeling results to show that if stubbornness is scientifically valuable, it still involves a willingness to change one’s mind. (shrink)

¿Qué tipo de agencia es necesaria para la personalidad jurídica? ¿Cuáles son los requisitos cognitivos y racionales que los sistemas legales asumen acerca de los sujetos de la ley? ¿Cómo es que los seres humanos cumplen con estos requisitos? En trabajo previo (Cáceres y Montemayor, 2016), hemos argumentado que estas preguntas requieren un nuevo acercamiento a la teoría del derecho, basado en hallazgos recientes en ciencia cognitiva, que van más allá de tratamientos teóricos neuro-legales contemporáneos. Aquí construimos sobre esta propuesta, (...) ahora enfocándonos en cuestiones de agencia y normatividad, incluyendo tipos de agencia que son relevantes para la epistemología social. La conclusión principal del artículo es que los muy estrictos requisitos cognitivos que se asumen sobre las capacidades explícitas de racionalidad de los agentes cognitivos, presupuestos por la ley, no sólo son incompatibles con los hallazgos en psicología, sino que un análisis sistemático de la agencia moral y epistémica también es necesario para poder entender la normatividad legal. El argumento principal es que tipos de agencia colectiva, moral y epistémica, difieren de la agencia individual, la cual también debe distinguirse como moral y epistémica. Fundamentalmente, la agencia colectiva difiere de la individual no sólo con base en diferencias con respecto a la racionalidad, sino también con base en los criterios de integración informativa. Varias consecuencias de este análisis son evaluadas, incluyendo aspectos concernientes a integración informativa para juicios y decisiones, comunicación fiable para la agencia epistémica, y la integración de consideraciones morales en el razonamiento jurídico. Una revisión comprensiva de la noción de “autonomía” es justificada por esta propuesta, en parte porque los requisitos comunes para la personalidad y autonomía jurídica son muy demandantes e inadecuados en muchos casos, y en parte porque la agencia colectiva debe tomarse en consideración como un tipo fundamental de agencia legal responsable para procesos de integración informativa. Basándonos en la distinción entre formas epistémicas y morales de razonamiento, explicamos cómo los sistemas legales necesitan de altos niveles de integración cognitiva para la responsabilidad legal a nivel colectivo. (shrink)

Después de enseñar la asignatura de Ética, y de la aplicar unas normas familiares escolares tradicionales, los estudiantes no se apropian de elementos éticos por varias causas: no les ven utilidad, no comprenden el contexto, o simplemente no les afecta, anulando cualquier interés al respecto. Esto impide que su obrar en la cotidianidad no sea tolerante en su ambiente escolar, generando dificultades en el docente para mediar comportamientos opuestos a una cultura de paz. Ante esto, se propone la Filosofía para (...) Niños (FpN) como apuesta ético-política que permita robustecer el pensamiento crítico, creativo y cuidadoso para mirar hacia una cultura de paz. Diego Pineda, el fundador de FpN en Colombia, sostiene que es necesario desarrollar en los estudiantes habilidades de pensamiento que, adicionales a conocimientos éticos-ciudadanos, los lleve a tomar decisiones acertadas en el abordaje pacífico del conflicto. El desarrollo paulatino del pensamiento, la cercanía a las comunidades de indagación, la incursión en habilidades cognitivas y éticas producto de las herramientas pedagógicas propias del programa de FpN, constituyen una preparación para asumir posiciones argumentadas frente a dilemas que acontecen dentro de los conflictos escolares, ello facilitará al estudiante estructurarse y lograr tomar decisiones iluminadas por la razón. (shrink)

Like non-verbal communication, paralinguistic communication is rooted in anatomical and physiological factors. Paralinguistic form-meaning relations arise from the way these affect speech production, with some fine-tuning by the cultural and linguistic context. The effects have been classified as “biological codes,” following the terminological lead of John Ohala's Frequency Code. Intonational morphemes, though arguably non-arbitrary in principle, are in fact heavily biased toward these paralinguistic meanings. Paralinguistic and linguistic meanings for four biological codes are illustrated. In addition to the Frequency Code, (...) the Effort Code, and the Respiratory Code, the Sirenic Code is introduced here, which is based on the use of whispery phonation, widely seen as being responsible for the signaling and perception of feminine attractiveness and sometimes used to express interrogativity in language. In the context of the evolution of language, the relations between physiological conditions and the resulting paralinguistic and linguistic meanings will need to be clarified. (shrink)

A recent article by Burch-Brown and Archer provides compelling arguments that biodiversity is either a natural kind or a pragmatically-valid scientific entity. I call into question three of these arguments. The first argument contends that biodiversity is a Homeostatic Property Cluster. I respond that there is no plausible homeostatic mechanism that would make biodiversity an HPC natural kind. The second argument proposes that biodiversity is a multiply-realizable functional kind. I respond that there is no shared function to ground this account. (...) The final, and strongest, argument, is that biodiversity is an ineliminable explanans and explanandum in various subdisciplines of biology. I argue that once we look at the details of the relevant research, not only does biodiversity in a broad sense not function in explanatory roles, but we must eliminate biodiversity in favor of more specific concepts in order to make sense of the leading explanations in contemporary ecology and conservation science. (shrink)

Statistical Default Logic (SDL) is an expansion of classical (i.e., Reiter) default logic that allows us to model common inference patterns found in standard inferential statistics, e.g., hypothesis testing and the estimation of a population‘s mean, variance and proportions. This paper presents an embedding of an important subset of SDL theories, called literal statistical default theories, into stable model semantics. The embedding is designed to compute the signature set of literals that uniquely distinguishes each extension on a statistical default theory (...) at a pre-assigned error-bound probability. (shrink)

This book traces the origins and evolution of cybersemiotics, beginning with the integration of semiotics into the theoretical framework of cybernetics and information theory. The book opens with chapters that situate the roots of cybersemiotics in Peircean semiotics, describe the advent of the Information Age and cybernetics, and lay out the proposition that notions of system, communication, self-reference, information, meaning, form, autopoiesis, and self-control are of equal topical interest to semiotics and systems theory. Subsequent chapters introduce a cybersemiotic viewpoint on (...) the capacity of arts and other practices for knowing. This suggests pathways for developing Practice as Research and practice-led research, and prompts the reader to view this new configuration in cybersemiotic terms. Other contributors discuss cultural and perceptual shifts that lead to interaction with hybrid environments such as Alexa. The relationship of storytelling and cybersemiotics is covered at chapter length, and another chapter describes an individual-collectivity dialectics, in which the latter constrains the former, but the former fuels the latter. The concluding chapter begins with the observation that digital technologies have infiltrated every corner of the metropolis - homes, workplaces, and places of leisure - to the extent that cities and bodies have transformed into interconnected interfaces. The book challenges the reader to participate in a broader discussion of the potential, limitations, alternatives, and criticisms of cybersemiotics. (shrink)

1. EI dilema de Jørgensen. 2. La salución propuesta. 3. Breve historia de un prejudicio filosófico. 4. Normas sin lógica. 4.1. Imperativos sin lógica. 4.2. Normas y proposicienesnormativas. 4.3. Proposiciones normativas y normas verdaderas. 4.4. Mundos posibles. 4.5. Validez e invalidez. 4.6. La racionalidad del legislador. 5. La noción abstracta, sintáctica y semántica de consecuencia. 5.1. La noción abstracta de consecuencia. 5.2. La noción sintáctica de consecuencia. 5.3. La noción semántica de consecuencia. 5.4. EI sentido dado por las reglas de (...) uso en un contexto. 5.5. Qué operadores para la lógica. 5.6. Solo en un contexto la parte cobra sentido. 6. La lógica deóntica. 7. De donde la solución del dilema interesa a toda la lógica. 8. Consecuendas para la informática. (shrink)

Standardly, the usual approach to rationality is based on the notion of ‘being a reason for’. Honouring the traditional distinction between practical and theoretical philosophy, reasons are classified as justificative and explicative. In both cases, a reason-statement has the form ‘’. For reasons of type , ‘A’ is a factual statement and ‘B’ is a statement which describes an action of the agent. The reason-statement has a prescriptive sense because ‘A is a reason for doing B’ means ‘A is a (...) reason an agent ought to do B’. So, it is advisable to schematize that kind of statements as ‘’, where ‘OB’ is a deontic statement prescribing the duty to do B. Reasons of type have a descriptive sense and do not require the above-mentioned constraint. But ‘being a reason for’ has different senses according to context, even when the distinction between justificative and explicative reasons is drawn. Accordingly, it is important to distinguish two basic types of reasons: sufficient and necessary, and two subordinate types of reasons: contributing and substitutive . A lot of attention has been paid, lately, to a sense of contributive reasons: prima facie reasons . The paper will deal with that kind of reasons. Its main thesis are: 1) prima facie reason-statements are defeasible conditionals ‘’ pointing out that A is a contributing condition of B, 2) a defeasible conditional has the properties of ‘’, where ‘ =>’ is a strict implication and ‘f’’ a revision-operator satisfying the conditions set up by the theory AGM on the rational change of theories. (shrink)