Why is Locke's Linguistic Theory Still Current and Interesting Today?

In the Essay Concerning Human Understanding (1690), Locke set out to offer an analysis of the human mind and its acquisition of knowledge still very current and important today. Locke offered also an empiricist theory according to which we acquire ideas through our experience of the world. The article examines L ocke’s views on language and his principal innovation in the field of linguistic theory, represented by the recognition of the power of language with respect to the classification of the world, and its relative independence from reality. In particular the following topics are discussed: a) the polemical contrast with Cartesian philosophy b) the criticism that Locke levels against innatism c) the function of abstraction of the mind d) the concept of semiotics as a theory of thought and its expression e) the radical concept of arbitrariness f) the pragmatic factor intrinsic to Locke’s linguistics described as “communicational scepticism”.


Introduction
The present article aims to illustrate the originality and importance of the Essay Concerning Human Understanding, published by Locke in 1690, by highlighting the innovativeness of its analysis of the functioning of the human intellect and of its intrinsic relation to language. This originality accounts for the profound influence the work exercised on the Enlightenment philosophy of language. The article will examine and discuss some of the fundamental issues addressed in the Essay: 1. the power of language with respect to the classification of the world, and its relative independence from reality; 2. the historicity and arbitrariness of linguistic signs, which Locke interprets in a way that is still relevant to the history of modern linguistic thought; 3. the theory of signs, which encompass both ideas, i.e. the content of the reflecting human mind (Phantasm, Notion, Species" I/I, 8) 1 , and words, i.e. the signs of these inner conceptions contained in the mind, which become associated with them to the point of replacing direct experience by virtue of the automatisms that social usage establishes between words and ideas.

The anti-Cartesian polemic
From the very first book of the Essay, aimed at refuting innatism, Locke closely engages with Cartesian philosophy, establishing a dialogue marked by elements of continuity, but also by criticism and disagreement 2 . For example, Locke agrees with Descartes that our existence is the primary certainty: "I think, I reason, I feel pleasure and pain: can any of these be more evident to me than my own existence?" (Locke 1690, IV/ IX, 3). However, unlike Descartes, Locke does not grant that thought is the essence of the soul; rather, he regards it as one of its functions or activities, which is sometimes at work and sometimes not. For Descartes, reason is a spiritual force that attains its highest degree of purity and self-sufficiency in intelligence, to the point that the philosopher identifies reason with the Divinity. Locke's perspective is very different, because he rejects this conception of reason as the shutting up of man within the realm of his own thoughts as a means to attain irrefragable truths. In its place Locke establishes secular reason, which is based on man's dealings with things, sets out from empirical data (provided by senseperception), and is constantly influenced by circumstances as well as by the economic and social conditions on which the possibility of receiving a good education rests (Locke, 1690, IV/XVII). From Locke's perspective, the use of rational operations never leads to definitive and irrefutable results; nor is this faculty identical in all men. Descartes (like Spinoza and Berkeley) denies that it is possible to understand the human spirit through the tools of immanent intelligibility, and affirms the dependence of human thought upon that of God, insofar as the former is only a reflection or miniature copy of the latter 3 . By contrast, according to Locke human consciousness must be analysed without making any reference to realities belonging to a higher order: it must be free from all theological implications. The rise of psychology, to which Locke provided a crucial contribution, was only ensured by the severing of this bond, which made it possible to scientifically investigate the psyche without the need for any reference to the spiritual model based on religious identity.
Locke's representation of individual consciousness as a tabula rasa, therefore, constituted a sort of initiation for psychology, which required the mind to be cleared of all pre-existing elements. Locke himself presented his work as a clearing process, as the removal of the scaffolding of metaphysics. He made no compromise with transcendence, so as to ensure an objective study of the principles and mode of operation of human intelligence. This study was exclusively conducted on the basis of a "historical plain method", where the adjective "historical" refers to a natural history inspired by Bacon.
Locke's philosophy, in other words, follows the descriptive method, which seeks not to investigate the essence, substance and substrate of phenomena, but rather to describe phenomena and symptoms, and to classify them in order to understand their mode of operation regardless of their essence. The very use of the term "symptom" betrays Locke's long-standing interest in medicine, an interest which he pursued both first-hand and through his friends' studies -for instance, Sydenham's theory about the interpretation of illnesses. Again in polemical contrast to Descartes, Locke suggests that instead of venturing into abstract research on what lies beyond experience and which therefore can only be inferred, we should keep to what manifests itself in our experience and can actually be analysed by reason, since to trace the limits of our capacity to judge things is precisely to consolidate the sphere within which it can legitimately be exercised. Thought is not transparent to itself: reflection makes us aware of our intellectual activity yet does not reveal its ultimate nature and essence. This way of framing the whole enquiry was later adopted by all Enlightenment philosophers. Hume, for example, fully agreed with this approach: he described his landmark work A Treatise of Human Nature (1739) as an attempt to introduce the experimental method of reasoning into moral arguments, and to apply the method of Newtonian physics to the mental space.
The criticism that Locke levels against innatism constitutes another significant difference compared to Cartesian philosophy: Locke rejects the belief that there are innate principles in the mind, which is to say principles that are explicitly or potentially present within it from birth: for example, the logical principle of noncontradiction ("A is not non-A"), mathematical principles (equality, proportion, etc.), and practical or moral principles such as the ideas of virtue, duty, goodness, and God. Locke's polemic against innatism rests on his belief that man does not possess any original or primary characters imprinted upon his mind from birth, because at the initial phase of its existence the mind is like a white sheet of paper, devoid of any characters or ideas (Locke 1690, II/I, 2). Only later, and very gradually, does the child start developing some ideas which do not entail anything innate but derive from just two sources or "fountains": sense-perception and reflection (or inner perception). There are no ideas in the mind except those which have been impressed upon it by these two sources constituting experience, which alone furnishes the "materials" of our reason. As later confirmed by the development of 18th-century epistemology -from Hume to Kant -there can be no use of the intellect apart from experience. Contrary to what Descartes maintains, reflection is part of experience: even though it is not really a sense, insofar as it has nothing to do with external actions, it is something similar, which is why Locke (1690, II/I, 4) describes it as an "internal sense".
In rejecting innate ideas, Locke does not at all deny that a child can develop ideas already in the pre-natal phase -for example, that before birth it can receive some ideas through the impressions left upon it within the maternal womb by certain objects, or by bodily needs and discomforts. In fact, Locke hypothesises that the ideas of heat and hunger probably fall within these so-called "original" ideas (1690, II/IX, 6). However, these should not be confused with the aforementioned innate principles, since they are still produced by some impression made on the body, which is to say via sense-perception, whereas the principles in question are assumed to be of a completely different nature from the body and indeed independent of sense-perception.
For Locke this refutation of innatism also has political implications, since it is associated with a criticism of the concept of authority. The rejection of the notion of innate and incontrovertible principles thus goes hand in hand with Locke's political and religious liberalism: And it was of no small advantage to those who affected to be masters and teachers, to make this the principle of principles -that principles must not he questioned. For, having once established this tenet -that there are innate principles, it put their followers upon a necessity of receiving some doctrines as such; which was to take them off from the use of their own reason and judgment, and put them on believing and taking them upon trust without further examination: in which posture of blind credulity, they might be more easily governed by, and made useful to some sort of men, who had the skill and office to principle and guide them. Nor is it a small power it gives one man over another, to have the authority to be the dictator of principles, and teacher of unquestionable truths (Locke, 1690, I/IV, 25).
Sense-perception lies at the origin of simple ideas that directly pertain to sensible experience, as in the case of the impression of a colour, or the perception of a flavour; they are suggested to -and not produced by -the mind, which progressively receives them, without playing any creative role. As correctly emphasised by Yolton (1985, p. 164-66), it is important to clearly grasp this concept of "passiveness", which has engendered so many misunderstandings. When Locke states that in receiving simple ideas the mind is passive, he is not saying that the stimulus reaches the mind without the latter coming into play at all, without the perceiving individual being active in any way. The very image of the mind in its original condition as a sheet of white paper on which nothing is written offers a clear alternative to the innatists' idea that the mind is full of ideas from birth, yet at the same time it proves misleading, if it is taken too literally and used to argue that the mind starts from scratch. In this whole section of the Essay, what Locke means by passiveness is involuntariness, whereby it is impossible for us to recall a flavour we have never tasted or to describe a colour we have never seen. When Locke states that the mind is inactive when a flavour or smell comes to our awareness, what he means is that the mind cannot exercise the kind of active power it exerts when we perform an intentional movement such as picking up a book, moving a hand or averting our gaze; in all such cases we are active in the proper sense, as we perform such movements by choice (Locke 1690, II/IX, 10). These simple ideas are the "materials" of all processes of knowledge, since the intellect stores, repeats or compares them, combining them into an almost endless array of complex ideas, such as the conceptions of "beauty", "man", "horse" and "gratitude".
For Locke the organisation of mental reality finds its regulatory principle in the notion of association of ideas, an expression that also occurs as the title of a chapter of the Essay (Book II ch. XXXIII). Through association, the elementary ideas, which are separate from one another, are organised into coherent wholes within our present experience, as well as through the remembrance of the past and the investigation of the future. This principle is also central to Hume's psychology, where it takes the form of a geography of the mind: the mind is seen as a flat surface whose layout can be determined with a fair degree of accuracy and reliability.
Upholding the dualism of body and soul, Descartes had argued that mind and matter do not share the same ontological nature. Locke derives linguistic consequences from this premise: representation is no longer considered to be analogous to what it represents, so that for example there is no longer any resemblance between a circle and the idea of a circle. Ideas are conceived as mental elements, as entities that cannot be spatially located; thoughts become signs of the same nature as phonemes: arbitrary signs. This break was to have momentous consequences for the modern philosophy of language: only on this basis was it possible to conceive language (and thought) as an arithmetical or algebraic calculation, as Hobbes, Leibniz and Condillac did 1 . The system of ideas or knowledge thus becomes a complex of historical-cultural choices that can never be laid out once and for all, since it is always open to change. The classes by which we classify the world do not correspond to the species that actually exist in nature. Therefore, we must abandon the illusion that ideas and names are guaranteed by real essences: the mind in mixed modes arbitrarily unites into complex ideas, such as it finds convenient; whilst others that have altogether as much union in nature, are left loose, and never combined into one idea, because they have no need of one name. It is evident then, that the mind, by its free choice, gives a connexion to a certain number of ideas, which, in nature, have no more union with one another, than others that it leaves out (Locke, 1690, III\V, 6).

Language and knowledge
Human experience as a whole falls within the sphere of signs, as regards both the subjective act of knowing and the inter-subjective act of communicating. Mental categorisation, therefore, is a semiotic activity in itself. According to Locke's way of framing the matter, semiotics is a theory of thought and its expression, since the activity of thinking can only take place in the mind if the latter has a material and sensible medium 1 . Signs are the means of ensuring this connection between the intellectual activity and the material element. For this reason, in the closing chapter of Book IV of the Essay, devoted to the distinction of three different species of science, alongside natural philosophy -which deals with the knowledge of things with respect to their essence, constitution and properties -and ethics -which instead consists in the search for those norms that make our conduct just and expedient -Locke posits semiotics, or the "doctrine of signs", which he identifies with logic: the third branch may be called Semeiotike, or the doctrine of signs; the most usual whereof being words, it is aptly enough termed also Logike, logic: the business whereof is to consider the nature of signs, the mind makes use of for the understanding of things, or conveying its knowledge to others. For, since the things the mind contemplates are none of them, besides itself, present to the understanding, it is necessary that something else, as a sign or representation of the thing it considers, should be present to it: and these are ideas. And because the scene of ideas that makes one man's thoughts cannot be laid open to the immediate view of another, nor laid up anywhere but in the memory, a no very sure repository: therefore to communicate our thoughts to one another, as well as record them for our own use, signs of our ideas are also necessary: those which men have found most convenient, and therefore generally make use of, are articulate sounds (Locke, 1690, IV/XXI, 4).
In such a way Locke reveals that the study of language can shed light on the workings of the spirit and that the analysis of ideas is necessary in order to understand their mode of composition and transformation, and at the same time to investigate the limits of the intellect. What is being inaugurated here is a line of philosophical thought apart from which even Kantian criticism would be unthinkable 2 .
Most of our vocabulary is made up of general terms and this, in Locke's view, is due not to chance, but to reason and necessity, given that a language consisting of personal names would exceed the limits of human memory. Moreover, the generality of a name ensures its intelligibility, enabling it to refer to ideas that are to some extent common to both the speaker and the listener: without general ideas and terms we would be left with a series of idiolects rather than a language. If all things in nature are particulars, then we can only experience this or that particular individual; however, in the vocabulary of languages words do not refer to particular entities, but designate more or less broad classes of meanings. This is the case, for instance, with the word "man", which refers to a whole class of individuals who fall within the common definition of man: For, since all things that exist are only particulars, how come we by general terms; or where find we those general natures they are supposed to stand for? Words become general by being made the signs of general ideas: and ideas become general, by separating from them the circumstances of time and place, and any other ideas that may determine them to this or that particular existence. By this way of abstraction they are made capable of representing more individuals than one; each of which having in it a conformity to that abstract idea, is (as we call it) of that sort (Locke, 1690, III/III, 6).
The concept of abstraction is crucial for the whole subsequent development of Locke's theory and had already been introduced in Book II: This is called ABSTRACTION, whereby ideas taken from particular beings become general representatives of all of the same kind; and their names general names, applicable to whatever exists conformable to such abstract ideas. Such precise, naked appearances in the mind, without considering how, whence, or with what others they came there, the understanding lays up (with names commonly annexed to them) as the standards to rank real existences into sorts, as they agree with these patterns, and to denominate them accordingly. Thus the same colour being observed to-day in chalk or snow, which the mind yesterday received from milk, it considers that appearance alone, makes it a representative of all of that kind; and having given it the name whiteness, it by that sound signifies the same quality wheresoever to be imagined or met with; and thus universals, whether ideas or terms, are made (1690, II/XI, 9).
Generality is the precondition for intersubjectivity, and hence for language itself, which necessarily comes into being through a process of abstraction. To abstract is to separate an element from its context: whiteness is never found in isolation, but represents that simple idea of a sensible quality to be found, for instance, in the milk we drank yesterday. Once we have done away with everything that connects the idea in question to that particular situation, it becomes representative of all the other similar qualities to be found across a wide range of elements we experience. The process of abstraction lies at the root of the formation of general ideas and of the signs that represent them, which is to say general terms (Locke, 1690, II/XI, 9). The function of abstraction of the mind, then, may be viewed as the criterion distinguishing human beings from animals: whereas according to Locke the other mental faculties (memory, discernment, and judgement) are common to all living beings, who no doubt possess them in different ways and to different degrees (1690, II/X, 1-2 and II/XI, 1-2), only the faculty of abstraction is proper to man. Hence, there are no grounds to rule out the possibility that animals have some kind of notion pertaining only to the particular ideas they have received from their senses (1690, II/XI, 11). This leads Locke to address the long-standing issue of whether animals have some kind of language. This is a particularly important topic, considering the theoretical context within which it had been raised by 18th-century rationalists: a context in which the Scholastic identification of rationality with the immortal soul was deeply rooted and in which Descartes -in his Discours de la methode (1637) -had upheld a clear-cut distinction between animals and men, denying the former any form of language and creativity 1 . Assigning animals a particular form of language, albeit a much less developed one -which is precisely what Locke does, by once again distancing himself from Descartes -means freeing reason from all theological scaffolding and regarding man as different from animals only by degrees rather than essence. It also means framing the relationship between body and soul in new terms, by considering the possibility that matter might exercise more than merely a passive function with respect to knowledge.
Generality or universality does not belong to the real essence of things but to the activity of the intellect. Here we can appreciate the difference between Locke's concept of abstraction and that developed by Scholastic philosophy, which he polemically opposes precisely because he does not believe that the human intellect can grasp the real essences of things. By creating abstract ideas and designating them with names, human beings "enable themselves to consider things, and discourse of them, as it were in bundles" (Locke, 1690, III/III, 20); and this aids the arrangement of representations and the way they are communicated. The general ideas thus formed are the nominal essences of things, which is all that we can know. The real essences of things -whose existence we must certainly assume, since they are the origin of the sensible qualities on the basis of which we distinguish and classify things -are unknown to us. If constant and indissoluble causal nexuses exist that run through the substantial structure of reality, these can only be identified by God's intellect, and not by man. In any case -and most importantly -they do not contribute to the mechanism of signification. For Locke -as for Hume -concepts are relations between ideas and not actual "materials".
For all these reasons, the concept of the arbitrariness of signs takes on a completely different significance for Locke from the one it had previously been assigned: instead of referring only to the indifference of the sound with respect to the thing it designates -and without concerning the concept itself, which actually serves as an intermediary within the general scheme of knowledge precisely because it is free from arbitrariness -it involves the formation and number of the ideas designated by the name, and which are found to be an arbitrary classification of reality. Locke thus questions the idea of the isomorphism between the linguistic level and the ontological one as the precondition for the existence of a non-arbitrary scheme of mediation. Whereas according to traditional metaphysics the relation between objects and the mind's knowledge of them is one of pure identity, given that the concept in the mind is the thing itself, according to Locke the relation between an idea and its external referent is purely nominal; although the nominal essence depends on and originates from the real essence, it is neither the same nor similar to it, but possesses a different character insofar as it is a sign or name. Acknowledging the problematic nature of the reference of words to things, Locke aims to overcome what -in his view -had been the underlying fallacy of Scholastic knowledge: the assumption that it is possible to attain reality starting from words, by envisaging reality as a sum of preordained meanings that only await to be assigned their respective linguistic signs.
The process of abstraction is a minimal one for simple ideas, whose names cannot be defined, since their definition would entail the breakdown of such ideas into simpler elements, which in turn could further be broken down, and so on ad infinitum. On the other hand, these names are the least controversial ones because they can be "explained" ostensively. The maximum degree of abstraction is instead to be found in relation to the names of mixed modes or relations that stand for combinations of ideas arbitrarily construed by men, and which therefore do not correspond to any real object in nature (as in the case of moral or juridical terms). Examples would be linguistic expressions such as "parricide", "sacrilege", "gratitude", "justice", "adultery", "homicide", etc. In the case of such combinations of ideas, the nominal essence and the real essence coincide. The name here is the only guarantee of the relative persistence and unity of the idea.
Abstraction, however, also comes into play in relation to the names of substances: for although these stand for complex ideas, which ought to correspond to real objects in nature, they are open collections that can constantly be enriched by new discoveries; hence, they do not constitute real essences that can be defined once and for all, in such a way to infer from their definition all the qualities and attributes of the corresponding objects. We thus use different names to distinguish water and ice, which are the same substance, yet do not do the same with molten gold and solid gold: this would not be possible if the nominal essences here coincided with the boundaries set by nature. Through ideas, or nominal essences, we certainly record characteristics that are concomitant in nature and the object of our perception; yet the choice of which and how many characteristics to make pertinent is arbitrary and contingent. Still, the fact that the procedures for the formation of ideas are arbitrary does not mean that they are unmotivated: on the contrary, Locke emphasises precisely the pragmatic motivations guiding our mind through this operation. What are established are only those ideas whose names human beings need, or which are useful for attaining knowledge. This theory of Locke will be confirmed by Jean Itard's writings documenting the program of linguistic re-education of Victor de l'Aveyron, a wild child found in France at the end of the eighteenth century 1 . Victor was inclined to connect each linguistic sign with one and only one thing located in some place. For example, to his eyes, the word book always denoted a particular book, the concrete object of his experience and not a member of the class of objects indicated by this linguistic sign. In other words, Victor could not understand the symbolic function of the linguistic sign: for him every word was a "proper name" and not a general term denoting a multiplicity of referents. Victor found it very difficult to understand and master the process of abstraction, so well described by Locke, the process which presides over the constitution of institutional signs and represents the precondition for inter-subjectivity.
Through the theory of general names Locke newly addresses the old-standing question of the establishment of genera and species. He adopts the critical and innovative position put forward by Robert Boyle, to whom Locke was connected by bonds of friendship and collaboration, as a prominent member of the Royal Society of Sciences -founded in London in 1660, also thanks to his contribution -and as the promoter of the Boyle lectures 2 . In 1666 Boyle had published the essay The Origin of Forms and Qualities according to the Corpuscular Philosophy, in which he criticised the doctrine of substantial forms and explained natural phenomena on the basis of the two great principles of matter and motion. Locke was strongly influenced by Boyle's conception of nature, even before fully devoting himself to philosophical speculation. Like Boyle, he wished to avoid introducing metaphysical assumptions in the study of science. Besides, in Locke's theory the very concepts of "idea", "substance", "primary quality" and "secondary quality" are defined in a way that is closely reminiscent, even from a terminological perspective, of the definitions provided by Boyle in his essay The Origin of Forms and Qualities (1666). Here, among other things, Boyle had affirmed the inconsistency of the Scholastic concept of form: form is not a real substance, but only matter itself regarded from the point of view of what might be defined as its "specific or denominating state"; hence, it is not the substantial form that distinguishes the various classes of bodies. And it is precisely the relative independence of nominal essences from the world that makes names the element of continuity by which the intellect can systematise notions; it is precisely the use of names that makes knowledge possible (Locke, 1690, III/III, 19).

Communication is a problematic process: a discussion
Collections of ideas vary from one interlocutor to the next, meaning that different people will have different "nominal essences" of the same object: collections of particulars that are not necessarily the same for all interlocutors. We thus have a full acknowledgement of the dynamic character of the nominal essence, which ultimately also configures itself as the meaning of the name. This nominal essence is the result of a conceptual choice designed to meet certain needs in terms of representation and communication, and conditioned by current linguistic usages. The emphasis is no longer on the stability of the relation between sign and concept, but on its unstable and ever-changing character.
The very possibility of communication is thereby always subject to the risk of misunderstanding, of incommunicability. It is very difficult to reach an agreement in discussions because the communication often occurs between subjects who use names with different meanings, as they attach different representations to the same words, which bear the imprint of their own particular way of being. In order to avoid misunderstandings, it would be necessary for the interlocutors to analyse the terms they intend to use, in such a way as to agree on their meanings beforehand and clarify the range of simple ideas encompassed by each complex idea. But this process is difficult to accomplish in the communicative praxis we all engage in. How, then, can we make ourselves understood when talking with others? Locke answers this questions by providing a pragmatic solution: we should talk as though the nominal essences were stable and identical for both the speaker and his interlocutor. This implicit pact is what enables all acts of communication; as it is not given once and for all, it must constantly be negotiated.
This problematic conception of communication, which sees it not as a linear, onedimensional process, but rather as an interactive process that often yields uncertain and contradictory outcomes, was to become common in the modern philosophy of language. Steiner (1981) noted that every communication process can therefore justifiably be regarded as a form of translation, which makes it difficult, if not impossible, to find two human beings that use words and syntax to mean the same things. Rather, each person will refer to his own cultural level and private linguistic repertoire, which reflects his unique and irreducible identity. The pragmatic factor intrinsic to Locke's linguistics -what Taylor (1992) has described as "communicational scepticism" -was later be taken up again by Hume, who assigned the imagination the task of bringing out the full semantic power of names: As the individuals are collected together, and placed under a general term with a view to that resemblance, which they bear to each other, this relation must facilitate their entrance in the imagination, and make them be suggested more readily upon occasion (…) Nothing is more admirable, than the readiness, with which the imagination suggests its ideas, and presents them at the very instant, in which they become necessary or useful. The fancy runs from one end of the universe to the other in collecting those ideas, which belong to any subject (Hume, 1740, p. 105).
The issue of communicational scepticism extends to that of the imperfections of words, which derive from the arbitrariness of our categorisation procedures -not from the arbitrariness of the sound of words. Hence they are proper to the names of complex ideas, rather than simple ones. Furthermore, these imperfections are found to the highest degree in the names of mixed modes, in particular ethical and political terms. Common usage is a sufficient factor of stability for ordinary discourse, but not for scientific discourse, where we must often resort to definitions in order to clarify the semantic range of the terms we are employing.
Semantic asymmetry manifests itself in an even more prominent way in the transition from one language to another. Natural languages themselves lead people to classify the world in contrasting ways. The differences between them are not just a matter of sounds and signs, but of world view. A comparison between different natural languages thus shows how practical motivations give rise to ideas of mixed modes which do not coincide -or only apparently coincide -from one language to another. This explains the diversity of languages, which according to Locke is a phenomenon intrinsic to the very nature of language and human cognitive devicesby contrast to a long-established tradition that, through the myth of the Tower of Babel, had seen this diversity as a divine curse or at any rate as a condition of inferiority to be overcome.

Conclusion
To conclude, it may be argued that Locke's Essay Concerning Human Understanding has the merit of analytically showing how our mind works with regard to the cognitive process and what a fundamental role language plays within it. The topics and problems that Locke investigates with originality and rigour concern important aspects of the contemporary philosophy of language and semiotics. For example: the semantic indeterminacy, the radical concept of arbitrariness, the function of abstraction of the mind, the theory of thought and its expression, the pragmatic factor intrinsic to Locke's linguistics that we can describe as "communicational scepticism" and the difference between human language and the communication systems used by animals. For this reason the Lockian philosophy continues to to be of utmost importance even for modern readers, making his thought open to promising future developments.