Digital and analogue Phenomenology

Phenomenology presents itself not as an explanation or interpretation of phenomena but as a description of them. Describing experience means making its internal structure explicit, which, in phenomenology, is an eidetic structure. The method of phenomenological explication or clarification is, however, by no means univocal. This paper aims to isolate the two fundamental ways in which phenomenological description is achieved. The first refers to a phenomenology of manifestation, based on the concept of determination or datum, which is realized in the phenomenological-static approach and, in particular, on the concept of extensive quality. The second refers to a phenomenology of disposition, based on the concept of tension or force – which is realized in the genetic approach as well as in Merleau-Ponty’s phenomenology of perception – and, in particular on the concept of intensive or forceful quality. The analysis of the difference between the two approaches allows us to introduce the crucial distinction between digital and analogue dimensions within phenomenology.

distinguish it from another tendency that I shall call (perhaps pleonastically) analogue phenomenology.It is necessary to adopt a sufficiently general viewpoint to illustrate these two alternative tendencies.
To this purpose, we can start with the fundamental question that underlies the distinction between the analogue and the digital methods, namely the question of what we mean when we speak of a phenomenological method.
The fundamental purpose of phenomenology is to provide a description rather than an explanation of experience.Phenomenology is therefore a descriptive science, as evident from the well-known principle of all principles, according to which.
Every originary presentive intuition is a legitimizing source of cognition, that everything originally (so, to speak, in its "personal" actuality) offered to us in "intuition" is to be accepted simply as what it is presented as being, but also only within limits in which it is presented there.We see indeed that each theory can only again draw its truth itself from originary data (Husserl, 1989: 44).
The phenomenologist must look at the world with eyes wide open.However, as any epistemologically aware philosopher can recognise, looking at the world with eyes wide open is an insufficient (though perhaps necessary) condition to provide an unambiguous and neutral description of experience itself.
Two considerations must be made here.The first is that any observational protocol (this is the lesson learned from the crisis of positivist and neo-positivist epistemology of Logical empiricism) expresses a description that inevitably requires theories, preliminary hypotheses, and a conceptual apparatus in order to be deciphered.From this point of view, providing a description of what manifests itself according to the ways it manifests itself falls under the well-known objection of epistemological naivety: there is no such thing as a neutral and objective datum.All data are conditional and to some extent (greater or lesser depending on the radicality of the thesis we adopt) hypothetical and theory-laden 1 .
The second consideration concerns the idea that a description of experience cannot be reduced to a simple inventory of the world.This is what Putnam calls the thesis of conceptual relativity (Putnam, 1988), which relates to the first thesis of the theoretical character of observation.The answer becomes manifold when it involves the seemingly natural and univocal question: how many objects are in this room?In fact, it depends on whether or not one considers material objects (the lamp, the chair, the book, the table), or extends the description to animate objects (such as myself), or to their parts (e.g. the pages of this book or my nose), or even the physical sum of the parts (the elementary particles of which those parts are made).This may even involve the mereological sum of the parts (this book is made up not only of its pages but also of the non-independent parts of them, such as the white of the paper), or even the sum of mereological sums (such as the book and my nose, understood as the result of the mereological sum of the independent and dependent parts that make them up).Further, if we also include logical objects, i.e. any constant that can be taken as the value of a variable, then our inventory of the world extends indefinitely.
Putnam believes that the answer to the question "How many objects are in this room?" is a matter of convention, since it depends on what we mean by object.If we were to regard a phenomenological description as an attempt to take inventory of the world, then such a description would prove not only naive but also inconclusive: there is no unambiguous way to take inventory or to report experience.
Husserl would provide the following reasons for these strong doubts about the neutrality and exhaustiveness of the descriptive method.The first is that the phenomenological method is not on the same level of experience as justification.In this sense, it is very difficult to accuse Husserl of endorsing a kind of myth of the given; that is, the identification of a neutral and autonomous plane of givenness or observation, whose non-linguistic, nonconceptual, and non-inferential nature would serve as the foundation for a higher theoretical and conceptual level (Soffer, 2003).Phenomenology is more than a strategy to control a belief system.Phenomenology is a strategy for making experience explicit.
What phenomenology shares with the thesis of the neutrality of observation is the fact that the notion of the given (or phenomenon) is not identified with the privative notion of semblance (Schein), understood as an illusory appearance opposed to actual reality, but rather with the positive notion of phenomenon or manifestation (Erscheinung).The given is characterised by effectiveness, positivity, and non-amendability.The relationship between given and concept refers not so much to a normative difference as to a difference in function and purpose.Perception, in both phenomenology and the Gestalt tradition, has its own laws (such as the law of contrast, or that of sufficient stability and differentiation) that are resistant to the properly conceptual and linguistic sphere.However, this does not imply a level of observability that can serve as a definitive justification for theoretical assertions or an epistemologically neutral and incontrovertible foundation.Quite the contrary.The observational dimension of experience presents, as we shall see later, a sign-like, non-obvious dimension that is an integral part of the evidence.
The second observation is that phenomenological description is in no sense an inventory of the world.Once again, the intention of phenomenology does not belong to explanation.It rather aims at the explication of the internal structure of the datum.Husserl considers such a structure as objective and essential, as capable of defining the notion of objectivity itself.
Phenomenological explication must also be distinguished from Carnapian rational reconstruction in the Aufbau (Carnap, 1967;Beaney, 2004).Carnap's method of rational reconstruction is in a certain sense specular to the phenomenological one: whereas the phenomenological explication of.
the datum means indentifying its structure, so to speak, from the inside, for Carnap such an explication consists in tracing, as Herbart (1964) puts it, a sort of arch that is realised in the extrapolation, starting from familiar but vague concepts (explicandum) of exact principles (explicatum), to then return, following such clarification and rational reconstruction, to the plane of the original datum which thus becomes transparent to thought itself.
In consonance with the analytic turn in philosophy, Carnapian rational reconstruction focuses on the conceptual-linguistic dimension of the overall system it can reach, i.e.its logical-syntactic and semantic components.The idea is that philosophical questions are not genuinely theoretical questions that can be solved in terms of truth and falsehood, but rather pragmatic questions concerning the choice of the best linguistic frameworks of reference.This explains Carnap's insistence on philosophical activity as conceptual engineering.
What I will try to show, starting from this general assumption, are two things.The first is that the phenomenological techniques for explicating experience are not unique.I will refer to two explication strategies: one originates from Husserl's static phenomenology (and is partially confirmed by Stein's perspective); the other that, stems from some schemes of Husserl's genetic phenomenology, as developed in Merleau-Ponty's perspective (Merleau Ponty, 1968, 2002, 2003).In turn, this draws upon Bergson's philosophy as its original matrix (Bergson, 1992), which represents, from our point of view, an alternative phenomenological approach to static explication.
The second thing I will attempt to show is that the first method of explicating experience, insofar as it is based on signs, constitutes a good basis for a certain digital description of experience, whereas the second method constitutes or attempts to constitute the basis for a genuinely analogue description of experience.

Digital phenomenology.
The first method of explication makes use of the notion of datum or givenness, which is considered primary.Something manifests itself and phenomenology has the task of describing its structure.
This structure refers to three fundamental notions.
The first is the notion of essence (Wesen) understood as a field of eidetic variation and therefore of invariance in variation (Husserl, 1983).The idea is that, in addition to an intrinsic variation and oscillation, experience manifests a substantial unity and, indeed, invariance.Without such an invariance, experience itself would lose its decipherability.The singularity of crimson red can vary into carmine red or vermilion red, thus preserving the red species, or it can be transformed (e.g. if subjected to particular lighting conditions) into blue or green while remaining within the confines of the colour genus.However, a colour can never turn into a violin sound, since this would violate the ontic structure of the colour region.
John, to take up Sellars' famous example (1956: 145), after installing an electric light system in his tie shop, can see the colour green in a tie that previously appeared blue under natural light.This recognition is conditioned, as Sellars himself points out, by theoretical acquisitions that regulate the correct circumstances for the attribution of a certain property; e.g. the fact that colours are observed in sunlight2 .
Colour cannot be transformed into a violin sound because the ontic structure of the colour region would then be violated.Therefore John cannot see the green colour turn into a high or low-pitched sound because this would violate the boundaries of the colour region, i.e. its potential for variation within eidetic boundaries.The internal structure of the given imposes that it always and essentially manifests itself according to invariances that unify the natural variations and oscillations constantly presented by experience.The result is the emergence of the concept of characteristic note, which was crucial not only for Husserl but also for the entire tradition at the time starting with Brentano and Twardowski.
In fact, the notion of characteristic note implies the notion of invariance and, at the same time, leads to the notion of determination, distinction, division (even if not separation), fragmentation (even if purely conceptual) of experience.We will see later how the centrality, in phenomenology, of the notion of determination as a qualified extension is decisive.
Ideation, unlike abstraction (e.g.empiricism)3 , intervenes in the presence of a single characteristic of the object and, in general, affects all known characteristics of the object separately considered.In short, in order to be able to speak of the given, it is necessary to presuppose an underlying ideational process.Moreover, ideation implies not so much a logic of concept formation as an internal explication of the nature of the datum.If it is deprived of its essentiality (phenomenologically understood as a unity of variations within the boundaries marked by material essences), then the datum could not be discriminated; it could not be experienced.
The second notion corresponds to the so-called material a priori (Husserl, 2001), i.e. to the foundational relations between non-independent parts of a whole (e.g.colour and extension).The fact that colour spreads in an extension is a law that pertains to the structure of the given as it presents itself, independently of any inference or conceptual acquisition.Moreover, the foundational relation does not involve the existence of a principle that is, so to speak, extractable with respect to the direct foundational relationship between the parts, but autonomously gives rise to perceptually independent wholes.If the concept of essence leads to the notion of characteristic note, then the concept of material a priori leads to the notion of independent part, which is the result of the necessary relationship (even if material or content-related) between non-independent moments or parts.
An independent unity exists only in the case of a connection between independent parts, as in the case of sounds in the unity of a melody, or in the case of colours in the unity of a chromatic configuration, that is, in all those cases in which it is possible to extrapolate and abstract a sensible form (a melody, for example) endowed with autonomy.
Relations of connection between "pieces" of a whole are factual relations; relations of foundation between moments are, on the contrary, essential and necessary.
In short, the existence of an autonomous or extractable content is not actually contained in the datum.The foundation relation, i.e. the phenomenological material a priori, involves neither the identification of an independent sensible form nor the existence of a unifying function of a conceptual or intellectual kind: it is in fact the elements of the datum which, in an intrinsic and autonomous way, are founded on each other, giving rise to independent wholes.
The third notion corresponds to the concept of synthesis, i.e. the identity of the object as its manifestations or its adumbrations vary (Abschattungen) (Husserl, 1966).The datum is structured in both a visible and an invisible dimension, which is nevertheless an integral part of the datum.All data have an implicit content that must be verified.Every object is by its very constitution an intentional object and must be examined only within the limits (and exactly within those limits) in which it is given in the intentional act.An absolute object, i.e. one that is in principle free from reference to a state of consciousness, is to all intents and purposes an absurdity.
This thesis, which we can call the thesis of the perspectival character of intentionality, maintains that every object manifests itself only through points of view and never in its entirety, that is, in its full adequacy.This thesis joins with a second one, which we can call the thesis of the synthetic character of intentionality.Such a claim shows how the perspectives through which the object manifests itself are presented as unified.The constitution of the object is based on the identification of appearances.
In the object, manifestations are coherent with each other and coagulate around a unitary pole, even if indefinitely open.However, this does not happen when the coherence is broken, as happens in hallucinations or in any interruption of the motivational mechanism that characterizes the regular flow of experience.The understood object, based on the inexhaustible interchange of synthetically organised perspectives, can be defined as an empty, i.e. non-substantial, noematic pole around which the indefinite appearances of it " turn ".
If the static version of the notion of synthesis points to the idea of the pole that allows the identity of the object to vary in its manifestations, then the genetic version of the notion of synthesis points to the important notion of motivation.The object is in fact conceivable as a synthesis of all possible determinations motivated by a present experience.The unitary synthesis to which Husserl refers is therefore neither a formal nor an ideal structure, but a structure substantially conditioned by content and "actual" elements.
An object is the same object if it establishes a motivational link with an initial, original appearance: in this sense, what is currently given motivates further appearances of the thing, from the sensible (the unseen side of the thing) to the more abstract and conceptual.
It is not necessary for a definite motivational link to exist: the synthesis of appearances can break down and that particular course of experience, that particular motivational link, can disintegrate.But it is necessary that some motivational link exists in order to speak of experience.This notion presupposes a cohesion and integration between the appearances that experience concretely offers.
It must always be kept in mind here that whatever physical things are -the only physical things about which we can make statements, the only ones we can discuss as being or non-being, being this or being-otherwise upon which we can disagree and make rational decisions -are experienceable physical things.Only experience prescribes their sense; and, since we are speaking of physical things, it is the actual experience itself that does so in its definitely ordered experiential concatenations (Husserl, 1983: 106).
The three notions of essence (in a phenomenological sense), a priori material and synthesis converge on a notion that is absolutely central to Husserl's phenomenology, namely that of determination, or characteristic note.
Experience is, for Husserl, essentially determined and any indeterminacy (i.e. when I hear a rustle in a bush) is ontologically dependent on something determined (it could be the movement of a dog or perhaps the blowing of the wind).
Phenomenology, as is well known, is a vague and inexact science that is very different from the formal exactness of mathematics and the material exactness of geometry.
But inexactness does not mean indeterminacy.In fact phenomenology, although inexact, is not indeterminate at all.Vagueness indicates the phenomenon's singularity, i.e. its inability to be unambiguously deduced from generality.On the contrary, vagueness indicates indistinctness, lack of focus, and opacity.While the former is essential and unavoidable for phenomenological description, the latter has no value in itself, but is always aimed at determination.Therefore, vagueness and inexactness on the one hand and indeterminacy or indistinctness on the other, cannot regarded as co-extensive.
Experience, insofar as it is structured and not a rhapsodic and disorganised chaos of sensations, is invariance in variation.If so conceived, the phenomenological method consists in offering experiential atoms (the red of that notebook, the profile of that shape, the sharpness of that sound, and so on) to description.They are meant as extensive parts of qualified experience in which one of the dependent parts (that of extension) plays a foundational role, albeit not defining, as it happens in the Galilean artifice.
Any object, in order to be experienced, needs an extension over which to spread.Extension is the condition of possibility for the appearance of a phenomenon or, being the same thing, the phenomenon needs an inscription within edges in order to manifest itself.On the other hand, as Husserl himself acknowledges, "the very essence of extension involves the ideal possibility of fragmentation" (Husserl: 1989, 33).
In this sense, since the explication that has been so far refers not to the actual parts of things but to signs that correspond to the actual parts of things, it can be interpreted as a phenomenological description of experience that we can call digital phenomenology.Here the instruments introduced (i.e. the concept of essence as invariance, of material a priori and of identity synthesis) are the means by which this digitalisation of experience can take place.

Analogue Phenomenology.
Here, I intend to argue that the concept of characteristic note or qualitative determination can be conceived not as an actual part of the thing itself, but as a sign (in the sense of Anzeichen, i.e. an index) of the actual part of the thing itself.
In the complex geography of the sign, the notion of characteristic note (and the underlying notion of determination) is neither conventional (in the sense that a flag is the sign of the nation, or a mark the sign of slaves); nor artificial (in the sense in which the rise or fall of mercury in a thermometer is an indication of body or atmospheric temperature).Moreover, it is not natural (in the sense in which fossil bones are the sign of antediluvian animals, smoke is the sign of fire, lightning is sign of thunder, the volcano the sign of Earth's magmatic state, or footprints in the sand an indication of the presence of an animal).The notion of a characteristic note, however, retains that sort of externality typical of the sign understood as an index in relation to actually lived experience.The concept of sign thus becomes inclusive of that of characteristic note and of the cluster of characteristic notes which, as Husserl himself states, are destined to make recognisable the objects to which they belong.In this process of discretization lies the transcription into signs (Bergson would say the inversion in the sign) (Bergson, 1992) of the continuum of experience.
The centrality of the notion of characteristic mark or determination is the result of a procedure similar to alphabetic transcription (Longo, 2015;Longo & Montévil, 2011, 2014), which contains in embryo a kind of digitisation of the phenomenological description of experience.The clarification of experience in terms of signs (i.e.characteristic marks) allows for the re-recognition of the thing and thus the possibility of acting on things and having a grasp on them.In this sense, the discretization of experience becomes an incentive for action.The thing itself, says Bergson, clearly anticipating Gibson's notion of affordance (Gibson, 1979), once inverted into a concept "turns towards me" and adopts a certain attitude "that allows me to have a grasp on it".
In short, concepts of invariance or determination (the result of the notion of Wesen); of element (the result of the notion of material a priori) and of identity (the result of the notion of synthesis), are not properly internal to experience itself but, as signs, are external to it.It is precisely this externalisation, together with the consequent discretization of experience, that produces what I have called digital phenomenology.This hypothesis offers the possibility of reading experience, if not in terms of quantitative determinations (numerical, measurable), then at least in terms of qualitative determinations; it is no longer numerical, but nonetheless discretizable, and therefore potentially, albeit indirectly, measurable.This is shown in Husserl's argument of the indirect mathematisation of plena (Husserl, 1970).
While this thesis distinguishes the realm of the qualitative from the realm of the quantitative, it also maintains, within the flow, a distinction between its units.The flow is indeed a continuum, but a continuum composed of units4 .
There is no absolute emptiness, i.e. absolute indeterminacy (except in the case of the absolute impossibility of determining something, as in the case of blindness or deafness from birth).This is the same as saying that absolute unactuality, or total background, does not exist.This is a confirmation, both for Husserl and Stein (Stein, 2004(Stein, , 2006)), of two fundamental factors: the first is the central role played by determination; the second is the impossibility for the single determination to "migrate" outside the eidetic boundaries, more specifically outside the boundaries of the eidetic generality.As Husserl himself acknowledges, if it is possible forfor the colour red to turn into yellow or blue, then it is not possible for a colour to turn into a violin sound.
The distinction between quantitative (mathematical) and qualitative (phenomenological) determination is intended to maintain the possibility, within the continuum, of distinctions of degree.But it is precisely the possibility of identifying, in the continuum of the flow of experience, distinctions of degree that transforms this kind of phenomenological explication into a digital phenomenology, capable of using signs that stand for concrete experience.
How is it possible to provide a description (and therefore an explication) of the flow of experience from within yet, without falling into the externalization of the sign concept of the characteristic note and the consequent discretization of the continuum of experience itself?
This attempt to truly satisfy the return to things themselves by describing experience from within, not as a collection of data or manifestations but as a qualitatively lived experience, is the great attempt (which I personally consider integrally phenomenological) of Bergson and, following him, Heidegger, Whitehead, Merleau-Ponty, and many others.If we were to trace this approach back to a theoretical core that distinguishes and characterises it as analogical phenomenology, then I would say that we can identify it in the replacement of the static concept of characteristic note with the dynamic concept of disposition, as well as in the replacement of the centrality of determination with the centrality of force or power.
Phenomenology can account for the qualitative dimension of experience in two ways: in terms of the (residual, signitive) concept that corresponds to qualitative determination, and in terms of the (original) concept of forceful qualities (Banks, 2003(Banks, , 2014)).

Determination versus disposition.
The phenomenological-analogue method of explication replaces the principle of manifestation with a principle that we might call the principle of tensionality.This principle characterises the genetic approach and the temporal dimension of phenomenology, being embodied in a cluster of constitutively dynamic and dispositional concepts such as those of motivation, sedimentation, passive synthesis, protention, retention, etc., all of which are used in the phenomenological-analogue method of explication.
The change in the method of explication inevitably entails a change in the concepts that characterise the so-called digital phenomenology.
The first concept, that of phenomenological essence as invariance in variation, has the function of isolating the notion of characteristic or determination.In analogue phenomenology the centrality of the notion of determination is replaced by the centrality of the notion of disposition (Heil 2005(Heil , 2010;;Munford 1998).Disposition, unlike determination, is independent of concrete manifestation, of actual realisation in a datum.Fragility, rigidity, malleability, ductility, and elasticity (but also temperamental states such as availability, or generosity) exist irrespective of the fact that they manifest in a concretely visible datum.Sensory content, according to genetic phenomenology, has its own capacity for organisation and structuring, independent of intentional form.Consequently, the method of phenomenological explication is not necessarily the explication of a datum that is already constituted and considered primary.The emphasis here falls on the motivational and sedimentation links that characterise tacit and passive experience.
In the dispositions, quality understood as what it is like or how it is with me (Nagel, 1980) is no longer residual but foundational.Sensation, far from being iletic material that offers itself to the shaping power of the intentional structure, is a primary affective dimension with an autonomous and founding efficacy5 .
This priority of the affective dimension is even more evident in the Heideggerian perspective.For Heidegger, hardness of a body can be traced back to the resistance of that body to the hand's contact rather than to a property of the body; just as it is improper to say that the chair "touches" the wall, since "the presupposition for this would be that the wall could have been encountered 'by' the chair" (Heidegger, 2010: 55), and being encountered in turn presupposes that openness and ambientality that only an experiential relationship can provide."Two beings, which are present in the world and are, moreover, worldless in themselves, can never 'touch' each other, neither can they 'be' 'together with' one another" (Heidegger, 2012: 56).
The second concept characterising what is known as digital phenomenology, that of material a priori, aims at isolating the notion of independent part (or element) from the foundation relationship between moments or non-independent parts by means of the instrument of distinctio rationis.In analogical phenomenology the centrality of the notions of distinction and element is replaced by the centrality of the notions of process and differentiation.
On the contrary, the essence of the process is the ideal possibility of a differentiation, a notion that implies a temporal model.
The third concept, that of synthesis, has the function of grasping the identity of the object as its perspectives, or adumbrations (Abschattungen) vary.In analogue phenomenology, the centrality of the synthesis (closely linked to the idea of constitution) is replaced by the notion of interweaving.
Feeling and flesh, both fundamental notions in Merleau-Ponty (1968), reflect the attempt to overcome the gnoseological and ontological predominance of closed notions such as determination, perspective and synthesis, in favour of open notions like those of intertwining, chiasmus, and reversibility between the internal and the external.Flesh will no longer be a mere thing, an extension covered by determined qualities, but living matter, "inwardly tormented", in which the word "alive" does not function as a predicate -that is, it does not denote a property or characteristic of matter -but rather corresponds to one modification of it.
The theme of the impersonal, which is so important to Merleau-Ponty precisely when it comes to sensation (traditionally and fallaciously conceived as the highest degree of subjectivity), is connected to the theme of historical or biological temporality.
Before Merleau-Ponty, Heidegger had acutely pointed out the risks of a determinative or categorical conception, noting the distinction between the practical domain of beingat-hand [readiness-to-hand] (Zuhandensein) and the theoretical domain of being-on-hand [presence-at-hand] (Vorhandensein) (Heidegger, 1992: 144).The clarification of the meaning of experience goes beyond the determinative question according to which "being" means being this and this.In fact, it aims to grasp that indeterminate and all-embracing precomprehension which constitutes experience itself, such us natural ambientality, median status (Durchschnittlichkeit), indifference, openness, non-aspectuality, and preliminarity.It aims at that indifferent preliminarity first of all and above all to which Heidegger makes constant reference in predicative terms.
In short, the analogical method of explication is based on the centrality of disposition (and not of determination), of difference (and not of distinction) and of interweaving (and not of synthesis).Indeed, dispositions enjoy a strictly temporal and historical status.Hence the context or environment (the non-actual spatial background) is not as essential to disposition as the background (the non-actual temporal background) is.So to speak, we deal here with sub-categorial dimension.
These general indications mark the boundary of an analogue phenomenology in which the description of experience is an explication from within experience itself and not a sign transcription of it by means of the concepts of invariance, element (or independent part), and synthesis.In the end, these concepts work to render experience artificially discrete by means of a representation that is, precisely, signitive (and in this sense, albeit metaphorically, digital).

Conclusion.
Digital transformation is inherent in a certain kind of explication of experience, based on the concepts of characteristic note, element and synthetic identity.Such concepts can be considered epistemological obstacles (in Bachelard's sense), as they shift the focus from things to the sign-like manifestation of things.A genuinely analogue phenomenology provides an explication of experience based on alternative and deeply dynamic concepts such as dispositions and powers; precisely those concepts legitimise, from an analytical point of view, the so-called genetic turn in Husserlian thought.
On behalf of all authors, the corresponding author states that there is no conflict of interest.
Funding Open access funding provided by Università degli Studi di Firenze within the CRUI-CARE Agreement.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material.If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.