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Antonio Livi


Alethic Logic and

the Epistemic Foundation

of Reasoning and Believing

Translated from the Italian by Peter Waymel

About the Author

Antonio Livi is born in Prato (Italy) in 1938. He was teaching Epistemology in several European Universities and he was the Dean of the Department of Philosophy at the Lateran University in Rome from 2002 to 2008. He is the founder and the current President of the International Science and Commonsense Association, and the Editor of  Sensus communis. An International Journal for Studies on Alethic Logic. The search for a new theory of truth on the principles of alethic logic is the main topic Antonio Livi is concerned with. His most known work, Filosofia del senso comune, originally published in Italian in 1990, has been translated into Spanish (1997) and in French (2002) and A second edition of this work, now translated into English, was published in 2010. Another Livi’s work already translated into English is Reason for Believing (Aurora, Col.: The Davies Group Publishers, 2008).


I wish to express my gratitude to my friend of long standing Philip Larrey, Ph.D., full Professor of  Epistemology in the Pontifical Lateran University, who helped me to evaluate the most useful suggestions furnished by several American analytic philosophers. I wish also to express my gratitude to José Meseguer, Ph.D., Professor of Informatics in the University of Illinois at Urbana-Champaign, who has contributed in rendering this English translation of my essay more faithful to the very sense of the original, even if not necessarily literal.


Chapter One

A Proposal for a New Philosophy of Common Sense

[1.1] Stating my intention

[1.2] Clarifications regarding the epistemological nature of common sense

[1.3] Clarifying the epistemic function of common sense

[1.4] Clarifications regarding the content of common sense

[1.5] Summary: what I intend to affirm with a philosophy of common sense

Chapter Two

Demonstration of my thesis on the existence of common sense

and on its epistemic function

[2.1] The object of the demonstration

[2.2] The logical-metaphysical presuppositions of the demonstration

[2.3] The method of the demonstration

[2.4] The carrying-out of the demonstration

[2.5] Carrying out the demonstration

[2.6] The specific arguments of the demonstration for each of the five truths of common sense

Chapter Three

Epistemological criteria that follow from the demonstration of the existence

and the epistemic function of common sense

[3.1] The demonstration of the existence and of the epistemic function of common sense furnishes the logical foundation of knowing

by means of inference, that is, of “science”, establishing at the same time its constitutive limit

[3.2] The demonstration of the existence and of the epistemic function of common sense furnishes the logical foundation of knowing

by means of testimony, that is, of “faith”, though only on the condition that the witness’s credibility be directly verified




Chapter One


[1.1] Stating my intention. – [1.2] Clarifications regarding the epistemological nature of common sense. – [1.3] Clarifying the epistemic function of common sense. – [1.4] Clarifications regarding the content of common sense. – [1.5] Summary: what I intend to affirm with a philosophy of common sense.

As is evident from the historical overviews which have been performed in the last years (cf. Mesolella [ed.] 2010), many exponents of modern and contemporary philosophy have deemed it necessary to use the term “common sense” during the course of their work. Moreover, they have used the term with a positive epistemic meaning, to vindicate the possibility of a realistic metaphysics of an anti-rationalistic, anti-skeptical nature. It is only with reference to these authors that we can affirm the existence of more or less embryonic or approximate forms of a philosophy of common sense. These incomplete discourses, grouped into two basic categories, allow me to state that some philosophers (not many, but important ones) have positively envisioned the value of common sense as a universal and necessary body of experience-grounded truths that constitute the absolute condition of possibility for both science and faith. Others (the larger part) have perceived a secondary though constitutive aspect of common sense, that is, its constitutive nature as the absolute condition of possibility for inter-subjective communication. None of these philosophers, however, has been able or willing to determine  the precise epistemological nature, epistemic function or contents of common sense. I therefore believe that a new, organic proposal of a critically sustainable definition of common sense would give a full value to the many scattered fragments of an authentic philosophy of common sense  existing in modernity, and even in our times. In an attempt to demonstrate the value of this precious wealth of positive intuitions, unifying and systematizing those scattered fragments, I now propose my notion of “common sense”. I will formulate this notion through ten basic theses.

[1.1] Stating my proposal.

I hold that the modern term “common sense” can still be used in philosophy today, if by it we mean primary evidences that constitute the “basic truths” for each thinking subject, due to their absolute immediacy (being, as they are, without presuppositions) and their function as an alethic foundation of thought in all its forms (being, as they are, the presupposition of every ulterior assertion with a claim to truth).

[1.1.1] My proposal in ten theses. – Although it will be necessary to duly deepen our research by returning repeatedly to the same theme – i.e., the different aspects of “common sense” – it seems to me appropriate to establish my proposal immediately in its essential terms. In this way it will be clearer which aspects of my analysis are obvious and given, which instead are debatable, as they are not universally accepted (these are those aspects which are polemical towards scientific rationalism and theological fideism) and which, finally, are universally ignored. It is these last two aspects that we propose to highlight and re-evaluate within the limits allowed by this study.  Here, then, are ten theses which summarize my new philosophy of common sense:

A first thesis is that there exists in human knowledge a realm of certainties that express what every thinking subject understands directly from experience, even before attempting to interpret – through reasoning – what he has experienced. Inasmuch as they are derived directly from experience, these certainties require no other epistemic justification than the absolute evidence that their object exists. Consequently, even when their object is reached through spontaneous inference, they manifest a decisively intuitive character; since the inference, in this case, is not a formal scientific reasoning, nor does it regard particular anthropological or cultural conditions.

A second thesis is that those certainties constitute our primary knowledge of concrete reality, that is, the awareness of the reality that de facto presents itself to every thinking subject (the “world-in-which-one-is” and one’s own “being-in-the-world” as a personal substance).  At the same time, in an indissoluble cognitive unity, they represent our primary knowledge of the universal, that is, that intuition of first principles, both those of a metaphysical-logical nature (which render essentially intelligible, though always problematic, the real from which and in which one lives) and those of a metaphysical-ethical nature (which reveal the meaning and significance of one’s own individual and social life, in both temporal and eternal perspectives).

A third thesis is that  such certainties, being connatural to human intelligence – that is, being a basic characteristic of human nature as such (at least as long as human nature has at its disposable the necessary material conditions to express itself in ordinary empirical life) – are the patrimony of all men and women, they are universal in time and in space, they are a constant in the midst of all the variables of culture and social conditions, just as they are a constant through all the variations (advances and regressions) of an individual’s intellectual developments.

A fourth thesis is that  this common basis of certain and indubitable knowledge – indubitable in itself, even if someone like Descartes can say (though not think) he has called them into question through meditative thought – is precisely what allows for the communication of knowledge among individuals. This communication begins with the acquisition of language and is further developed through the educational process and the relationship between parents and children in the developmental age. It also allows for communication of knowledge among different cultures, overcoming (at least potentially) the barriers of incommunicability resulting from the psychological, anthropological (both ethnic and political), philosophical-religious and technical-scientific differences, which, along with the historical component, characterize the various linguistic structures (of meaning and of significance).

A fifth thesis is that those certainties are in direct relation to philosophy, especially to philosophy as metaphysics; they are in all respects coextensive with metaphysical discourse, except for its scientific dimension (of reflection, of hypothesis, of the elaboration of conceptual definitions and logical derivations). The certainties derived so directly from experience are the very material of philosophical reflection, and also the perennial substance of its truest scientific conclusions, those which over the centuries – considering philosophy in its historic dimension – have allowed us to speak of a philosophia perennis.

A sixth thesis is that those same certainties are the condition of possibility (ex parte obiecti, since they furnish the universal objective horizon from which the specific formal object is extracted) of all particular sciences: sciences of nature, mathematical sciences, human or social sciences…  But, in addition to furnishing the sciences with the objective premises of scientific research, that is, the field of objective reality (presupposed as real and rational) to be delineated and analyzed, those certainties of which we speak are also the “human” premises of scientific work. They are the necessary conditions for exercising such sciences, and therefore the conditions of possibility ex parte subiecti: because they furnish the basic reasons, they make it possible for man to be a scientist, and also furnish the basic logical instruments (the principle of identity and of non-contradiction, the principle of causality, the principle of finality, the possibility of induction and of deduction…).

A seventh thesis deals with the different quality of common sense and science. I maintain that the organic body of certainties of which I speak is in itself qualitatively superior to science, including within the notion of “science” both the metaphysical as well as the particular sciences, that is, all reflexive and systematic knowledge, mediated by reasoning and by culture and equipped with its own technical methodology. The superiority of those certainties lays precisely in the quality of the certainty itself. While the certainty of those direct and universal statements is unconditional and absolute, scientific certainty always has limiting characteristics: either it is a subjective certainty linked to privileged conditions of experience or intellectual capacity; or it is a certainty available only to members of a specific cultural community equipped with its own research instruments; or it is a certainty that can be reached by all humankind, only in relation to particular historical events, or a certain historical level of technological development, or a particular historical perspective on human events; or it is a provisional (hypothetical) certainty, susceptible of falsification or at least revision and adjustment, when it is not a bold working hypothesis of an instrumental nature (that is, as an efficacious tool for research, for science itself, or a mere instrument at the service of technical work or other practical ends). To sum up, while the certainties of direct experience are (per se) incontrovertible, the certainties of science are (per se) debatable, or at least relative, perfectible, revisable; the former belong to all people at all times, the latter belong to some people and only in specific moments of personal or collective history. Secondly, the superiority of these certainties over science is also a primacy in truth: they come first, both logically and chronologically (because every reflection presupposes some direct knowledge to which to return, dealing as we are with secundae intentiones), and are also elevated above other certainties, in the sense that they cannot be contradicted (by the truth; that is, proven false), to the point that every scientific thesis that contradicts those certainties is for that very reason vitiated by error (even if that error can only be demonstrated at the level of science).

An eighth thesis deals with the relationship between particular sciences and metaphysics. I think that a dialogue between particular sciences and metaphysics is certainly necessary, and de facto always beginning anew. However, the threats of reciprocal interference or methodological commingling can be avoided, as can attempts to annex one to the other, deriving from epistemological errors (as in the age of classical philosophical cosmology or the age of modern positivism) if a basis of conceptual agreement is found. This basis can be done precisely by returning to the common epistemological derivation of the certainties and contents of direct experience, thus circumventing any attempt at an impossible, unmediated translation (without the mediation of those basic certainties) of the technical language of metaphysics into the technical language of the other sciences, or vice-versa.

A ninth thesis deals with Christian as concerned by the notion of common sense. I refer, indeed, to faith in its supernatural meaning, as understood by Catholic theology, that is, as a human, rational act.  Actually, Catholic theology defines faith as a full and certain intellectual adhesion to the truth revealed by God (transcendent truth, and thus non-evident to man in his present earthly condition), on the basis of the authority of God himself who reveals it. But this is possible just because man – every man – possesses the natural truths that are the necessary presupposition of the supernatural truths (praeambula fidei). Now, these natural, universal truths that are necessary (for faith) are precisely the object of the certainties of direct experience, and therefore we must underline that they are the conditions of possibility of faith (naturally, only from the epistemological point of view, without entering here into the problem of the moral dispositions of the subject). Furthermore, they are so as such, and not as formalized and then elaborated in scientific theses by philosophy. In addition, there also belongs to those certainties the task of passing from the praeambula fidei (the phase of mere potentiality) to the evaluation of the “reasons of credibility” (the phase of actuality of the act of faith), the first of which is the non-contradictory and fitting nature of each of the truths that are the object of Revelation. This is allowed, moreover, by the fact that Revelation – in having to address all men –  has necessarily used not the language of a particular culture or the language of the sciences (even philosophy), but rather the language corresponding to the notions of direct experience and their respective certainties (though clothed with the garment of the languages lent by the various historical cultures relative to the sacred writers and Tradition).

Finally, a tenth thesis deals with the relation between natural reasoning and believing in a supernatural revelation. If the certainties of common sense are the conditions of possibility of believing in any testimony, then, in consequence, the relation between reason and faith in Christian Revelation can not be reduced to the relation between philosophy and faith, though this relation is necessary and inexhaustible. Rather, it must be traced back to the epistemic background constituted by the certainties of direct experience, which, being common to all thinking subjects, are for all persons the necessary logical condition of possibility for revealed doctrine to be always understood and then possibly accepted through faith by some.

[1.1.2] The essential meaning of my proposal from the twofold point of view of the logic of assent and the logic of consent. – The nucleus of these ten thesis is that in all thinking subjects the search for the truth, in its entirety, leads back to the primary evidences that constitute “common sense”. They have a fundamental epistemic value for the individual subject (the logic of assent), independently of their communication to subjects through language and therefore independently of their being shared (the logic of consent). Such sharing, moreover, must necessarily take place, at least at the level of the consciousness of each subject implied in the processes of communication, because the primary evidences that constitute common sense are there from the very beginning in the mind of all thinking subjects. It is possible, however, for them not to be communicated through language; and then, when they are communicated, they may not be the object of formal assent: this is the (negative) characteristic of the critical encounter between subjects. They may be formally unaware, even at the most sophisticated levels of logical discussion, of the epistemic foundations of their discourse. Or, though recognizing their existence, they may be unable to trace the discourse back to them (see in this regard Pieretti 1973; see also Vorobej 2006; Walton 2006).

Therefore, for the purpose of further clarifying the meaning and range of my proposal, I will highlight some formal elements, with the intent of revisiting their fundamental nucleus later on:

i) As the result of a rigorous phenomenology of consciousness – which makes use both of subjective introspection and the analysis of the language with which inter-subjective dialogue is carried out – it is shown that in every thinking subject there are existential certainties whose epistemic justification is founded on the perception of that which necessarily and always presents itself in everyone’s experience as something evident.

ii) Such certainties constitute the very first link in the chain of presuppositions; for this reason they can in no way be subject to doubt. On the contrary, their non-truth is absolutely unthinkable: no one can ever really doubt them, and one must understand that any affirmations to the contrary, which might be found within a philosophical discourse, are merely verbal posturing: actually, they respond to some pragmatic logic, and not the expressions of a complete thought, that is, a real certainty, endowed with its own adequate epistemic justification.

iii) Given that they constitute the nucleus of experience, understood as a body of unmediated knowledge, such certainties are present to consciousness (though not always in an explicit manner) in every moment of the search for truth as the logical presupposition of all knowledge deriving from reflection and inference, both inductive and deductive.

iv) For this same reason, such certainties function as an ultimate criterion of truth to verify any hypothesis successively formulated. They therefore constitute the main alethic presupposition, that is, the presupposition necessary for any ulterior knowledge to be thought of as true. In fact, on the basis of these original truths, every thinking subject verifies, time after time, the admissibility of any hypothesis – formulated by himself or proposed by other subjects through one of the ways for communicating thought – that presents itself in the search for other truths over the course of his lifetime.

v) As a result, philosophy, too, and all scientific knowledge, should be structured logically as systems compatible with the primary truth of common sense (that is, with the primary certainties that constitute it), so as to place the instruments of dialectics (reflection, interpretation, inference) effectively at the service of the search for further truths.

I recognize that such a proposal – so demanding, and already strongly contested by many (cf. Di Ceglie 2005; Larrey, ed., 2008; Livi, ed., 2010) – cannot be merely stated but must be proven with a pertinent, adequate and rigorous argument. This is just what I shall do presently. Firstly I shall offer a proper logical demonstration (see §§ 2.1-4), and secondly I will cite the various types of confirmation that philosophy and the human sciences are able to furnish (see §§ 3.1-2). However, before proceeding to both parts of the demonstration, it seems to me necessary to specify further the meaning of my proposal, stating the specific characteristics I attribute to common sense, both from a formal point of view (the epistemological nature and the epistemic function) and from a material point of view, that is, the contents (and here I shall have to specify what I consider to be, concretely, the primary truths that make up common sense).