Logic, Methodology and Philosophy of Science
August 22, 1995, Florence, Italy
In a world of ever growing specialization, the idea of a unity of science is commonly discarded as an impossible ideal. Yet, at the same time, co-operative work involving cross-disciplinary points of view is usually encouraged, both as a remedy against the conceptual poverty of the scientific reductionism inherited from the Vienna Circle, and at the same time as a way of efficiently tackling the most stubborn and still unresolved problems which our society is facing today. The generation of knowledge is commonly perceived as a strange mixture of hard team research and individual imagination, a mixture which calls to mind the common expression: ninety per cent perspiration and ten per cent inspiration. Well, the aim of my paper is to suggest a better version borrowed from Susan Haack and to speak of a hundred per cent of "peirce-piration". With that purpose in mind, my paper will be divided in three sections: 1) a short presentation of Peirce; 2) a report of the history of the metaphor of the Tree of Knowledge and its application to the branching of science; and, finally, 3) an approach to the natural branching of science according to Peirce, who emphasized communication and love as key elements in the effort to achieve a real interface between the various sciences.
1. Charles S. Peirce (1839-1914)
Charles S. Peirce, the founder of pragmatism, not only identified one century ago that paradoxical situation that I have just briefly described, but also mapped out some paths that we could follow in order to get a clearer view of the problem and to really improve the communication between the various sciences. Peirce was a traditional and systematic philosopher. But his philosophical insights into the modern problems of science, truth and knowledge arose from the very valuable personal experience in the fields of logic and experimental science which he had gained in the bosom of an international community of scientists and thinkers (Hookway 1985, 1-3). His sound knowledge of the history of science and of the history of philosophy helped him in establishing a general cartography of scientific methodology.
Having been trained as a chemist at Harvard, and having done research in astronomy, mathematics, logic and philosophy, Peirce tried to disclose the common links between the various kinds of scientific inquiry and this in spite of their very different professional labels. Unfortunately his study of scientific methodology was pigeon-holed under the general title of "Classification of the Sciences", which is usually considered the despicable domain of librarians or academic administrators. But a closer study of Peirce's conception of science as a collective and co-operative activity of all those whose lives are animated by the desire to find out the truth and by "an impulse to penetrate into the reason of things" (CP 1.44; MS 615), may enable us as DeBrock has stressed to identify him as a true philosopher for the 21st century.
In Peirce's work there not only is a development of themes that run parallel to those found in the work of Frege, Russell or Wittgenstein, but there is also the framework for an integrated theory of culture (Hookway 1985, 120). Peirce identified the community of inquirers as essential to scientific rationality (CP 5.311). The flourishing of scientific reason can only take place in the context of research communities: the pursuit of truth is a corporate task and not an individual search for foundations. This framework "not only challenges the characteristic Cartesian appeal to foundations, but adumbrates an alternative understanding of scientific knowledge without such foundations" (Bernstein 1983, 71-72).
2. The Tree of Knowledge
The relationship between the generic unity of science and its several branches used to be expressed by the old metaphor of the "Tree of Knowledge". This is not only a beautiful metaphor suitable for engravings, but I think that it suggests a way to recovering the unity of science, because it expresses very well that "science as Peirce liked to put it is a living historic entity" (CP 1.44), that science is "a living and growing body of truth" (CP 6.428).
Perhaps it is useful to notice that there are three different metaphorical trees. The oldest one is the Tree of Knowledge from Genesis 2,9. Philosophers, however, are better acquainted with the Tree of Porphyry: the tree of genus and species, born in the FifrteFifteenth century, discussed by medieval logicians and often represented in Medieval and Renaissance books of logic. Both trees are mentioned in Peirce's Collected Papers (CP 3.488, 2.391 and 5.500), and on the latter one he wrote the entry for the Baldwin's Dictionary. But neither one is the tree I want to refer to. The tree that has my preference is the Arbor Scientiae which was made fashionable by Ramon Lull in the XIIIth century and which for many centuries has been the most common metaphor of the genealogy of sciences. According to this metaphor, all sciences are begotten from the common trunk of philosophy, which provides their underlying unity. The metaphor survives until now in the common usage of the expression "branches" to refer to the different areas of science.
It is well known that Francis Bacon employed that metaphor in his De Dignitate et Augmentis Scientiarum (1623) and distinguished two trees, the Tree of Human Knowledge and the Tree of Divine Knowledge. But perhaps the most interesting point is that Bacon's classification of sciences was based on a natural point of view. When he chose the three faculties of the soul (memory, imagination, and reason) as classificatory principles of arts and sciences, he was following the Galenic medical tradition which located each one of these faculties in one of the three ventricles of the brain (Tonelli 1991). One hundred and fifty years later, D'Alembert in his Discours prliminaire to the Encyclopdie (1751) expanded and up-dated the Baconian scheme with only a few modifications, but what for us now is more important he obscured its genealogical and historical character (Kelley 1991): "The encyclopedic arrangement I am quoting D'Alembert does not suppose that all the sciences stem from one another. They are branches which grow out of the same trunk, that is, out of the human intellect" (D'Alembert 58). The order of the encyclopedic tree is entirely conventional. The shift of emphasis is illustrated by D'Alembert's suggestion that the metaphor of the tree of knowledge be replaced by "a more exact image" of the classification of the sciences, namely the metaphor of a map of the world which can be drawn according to very different systems of projection.
Peirce carefully studied upwards of a hundred different classifications of the sciences and made many attempts to work out his own general classification of the sciences, as so many branches and sub-branches of a tree, springing out of one another (CTN 3, 217; L75; HP 805, 1124). Although he supported Auguste Comte's view of each science as a historical development, he disliked Comte's metaphor of sciences forming "a sort of ladder descending into the well of truth, each one leading on to another, those which are more concrete and special drawing their principles from those which are more abstract and general" (CP 2.119), because the image of an epistemic ladder of sciences (CP 1.180ff; Kent 1987, 71-72) suggested reductionistic tendencies similar to those of the twentieth-century positivist philosophy of science.
He preferred a natural classification, that is, one which embodied the chief facts of relationships between the sciences that "we have learned from observation" (CTN 3,170-1, MS 1334). Indeed, because a science is the actual living occupation of an actual group of living people, it is a natural object (MS 1334). Therefore, a natural classification must exhibit the living relations between the different branches of the tree, between the different traditions of inquiry.
3. The natural branching of science
According to Peirce, "sciences must be classified according to the peculiar means of observation they employ" (CP 1.101). "It is not what they have already found out which makes their business a science; it is that they are pursuing a branch of truth according to (...) the best methods that are known at the time" (MS 1334). Those "[w]ho pursue a given branch herd together. They understand one another; they live in the same world, while those who pursue another branch are for them foreigners" (CP 1.99, ca. 1896). Human reasoning is not a Cartesian search for foundations, but a co-operative and fallible vital activity of inquiry: "I do not call the solitary studies of a single man a science. It is only when a group of men, more or less in intercommunication, are aiding and stimulating one another by their understanding (...) that I call their life a science" (MS 1334).
Sciences are rooted in the observations of many men (CTN 3, 228). "Men who spend their lives in finding out similar kinds of truth about similar things (...). They are all familiar with words which others do not know the exact meaning of, they appreciate each other's difficulties and consult one another about them. They love the same sort of things. They consort together and consider one another as brethren. They are said to pursue the same branch of science" (HP 804-5). Each community of scientists grows around some specific ways of perceiving, some special methods of research. In particular one thing which commonly unites them is their common skill, not possessed by outsiders, in the use of certain instruments, and their common skill in performing certain kinds of work (MS 1334). Each science corresponds then to a special kind of observations which renders peculiar the modes of thought of the students of each special branch (CP 1.100).
In his classification, Peirce was guided by "how scientists associate themselves into societies and what contributions are commonly admitted into one journal" (L75). In his later years Peirce, who was living isolated in Milford, Pennsylvania, stressed the link between the genuine desire to learn and to discover truth, and some "imperative need of finding in nature an object to love". Moreover he stressed that scientific creativity originates in the germinal tissues. Not only that "... the higher places in science in the coming years are for those who succeed in adapting the methods of one science to the investigation of another" (HP 1882, 942), but that new knowledge is generated wherever communication is enhanced (HP 805-9).
In my view, contemporary relativistic trends can be considered as a reaction to the shipwreck of scientism of the Vienna Circle, and to Neurath's failed attempt at an International Encyclopedia of Unified Science. The unity of science is not achieved by the reduction of special sciences to more basic ones, nor can it be provided by a general semiotic conceived as a scientia generalis. For Peirce, "science does not advance by revolutions, warfare, and cataclysms, but by cooperation, by each researcher's taking advantage of his predecessors' achievements, and by his joining his own work in one continuous piece to that already done" (CP 2.157). The key to the advancement of knowledge and to the development of sciences is not revolution, but growth in a very peculiar mixture of continuity and fallibilism.
In contrast to science which grows upon special experience, philosophy is precisely "that science which limits itself to finding out what it can from ordinary everyday experience, without making any special observations" (HP 825). For this reason, philosophers are in a better position to call for a unity of the sciences. But, seen from a Peircean perspective, the articulation of the branches of knowledge is simply the effect of the efforts of a real community of human beings trying to share their discoveries. It involves the commitment of each scientist to bring together into a single field of activity the universe of ordinary experience and the universe of scientific experience. In some sense, this is a matter of attitude and a matter of method: what "constitutes science, then, is not so much correct conclusions, as it is correct method. [And] the method of science is itself a scientific result. It did not spring out of the brain of a beginner: it was a historic attainment and a scientific achievement" (CP 6.428).
The attitude of the scientist consists in aiming at unity while clearly respecting the autonomy of each science and the special method of each branch of truth. It involves a definite trust in the capacity of human reason to provide a general understanding, however provisional, and to establish communicative links with others.
It is not altogether incongruous to follow Peirce's tendency to translate his important insights into solemn phrases, and to translate this dream of science which he developed during his last years in Milford into the expression: "The Law of Reason is the Law of Love". The real articulation of the sciences will be achieved by pursuing a common goal from a plurality of specific methods, provided it be illuminated by the throbbing unity of everyday experience from which every true philosophy is born.
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