The Realm of Science
Regarding the knowledge of the physical world (or “Nature” for brevity) pre-modern philosophy shared a generalized ontological realism: Nature consists of a display of “substances” existing in themselves and independently from human knowledge.
These substances have properties and relations that have no independent existence because they exist only in the substances, but are independent from our knowledge as well. We can know a substance only by knowing its accidents, which appear to us, whereas the substance has an essence which we try to know in our endeavor to understand and explain the appearances (often called phenomena). Therefore, the appearances were not understood in the negative sense often implicit in ordinary language, as something misleading: appearances were what is manifest of reality, and for this reason a commonly accepted methodological imperative was that of “saving the appearances” (or “saving the phenomena”): therefore, that was also a position of epistemological realism regarding the phenomena, that aimed at being extended also to the substances, by inferring the knowledge of the essence from the knowledge of the accidents.The scholastic philosophers were aware that there are different possibilities of “saving the appearances” by proposing what today we would call models, or images, or representations of the underlying substance, so that the selection of the correct representation had to be secured by means of much more fundamental and broader philosophical considerations.[1] For this reason they distinguished—e.g. in astronomy—the models that could make easier the calculation of the celestial movements (and were used by the ‘mathematical astronomers’) from those which were considered to be true representations of the real structure of the universe (and whose elaboration was the task of the ‘philosopher-astronomers’).
When Galileo, thanks to his astronomical discoveries, was convinced that the Ptolemaic system was wrong, he admitted that the rival Copernican theory was true and attributed to Copernicus himself this persuasion, against those who maintained that he had only wanted to offer a more efficient mathematical model.[2] This was also the position of Newton, who explicitly used the term “phenomena” in the sense of what is “manifest”, while refraining from admitting in the natural science the “hypothesis” of “hidden qualities” allegedly belonging to the essence of the physical bodies. The impressive harvest of discoveries rapidly acquired by the new natural science of mechanics convinced scholars that this was at last a model of what science in general should be and this is the well-known declaration made by Kant in the Preface to the second edition of the Critique of Pure Reason.How could that cognitive success be explained? Half of the answer was given by Galileo himself when he explicitly proposed to restrict the investigation of the physical bodies to the study of a few accidents (called by him “affections”) giving up the pretension to capture “by speculation” the intimate essence of bodies.[3] This position was shared by Newton as well. The second half of the answer consisted, in the case of Galileo, in a selection of those ‘accidents’ that could be the target of investigation, and he discarded those that are ascertained by sense perceptions (and as such depend on the peculiarity of the sense organs), limiting scientific research to those “real accidents” that are mathematically expressible. From this followed that the “great book” of Nature is written in mathematical characters and can be red only by using mathematics. Coming to the concrete application of these proposals, the study of a physical phenomenon consists in formulating a “supposition” about its structure by proposing what we would call in modern terms a ‘mathematical model’ of it, and then artificially preparing an experimental set up in which this model is tested.
If the test is negative, the model (though mathematically sound) is rejected; if the test is positive, this model is accepted as a representation of the true structure of that phenomenon.[4] In this balanced synergy of empiricity (“sensible experiences”) and logos (“mathematical demonstrations”) one easily sees the relevant cognitive role attributed to reason: the mathematical conjectures are not the result of empirical generalizations, but are introduced by reason and are the prerequisite of the experiment. Moreover, a great achievement such as the principle of inertia introduced by Galileo was attained by a chain of logical arguments, despite the fact that empirical generalization would have led to its rejection, since there is no one single case in which we can observe that a body on which no force is acting remains in a state of rest or indefinite rectilinear motion. Owing to the above sketched reasons Galileo inaugurated modern natural science according to the ontological and epistemological realism of the tradition.This ‘second half of Galileo's answer is only partially shared by Newton. The concrete construction of his physics remained substantially in keeping with the Galilean approach, but with some not negligible differences that can be qualified as the expressions of his rather strict empiricism. For instance, mathematics remained in his work a powerful methodological ‘instrument' for the rigorous presentation of the physical knowledge but without any ontological commitment, and in his famous Scholium Generale of the Principia he discarded hypotheses that pretended to be more than propositions “deduced from the phenomena” and “generalized by induction”.[5] Despite this, he made various efforts in his other investigations in order to find out some ontological ground for the explanation of the property of gravitation but unsuccessfully, so that we can say that he was an ontological realist (since admitted that science investigates a reality independent of our cognition) but an epistemological agnostic (since he remained doubtful about our possibility of going beyond the ascertainment of phenomena). Nevertheless, he cannot be qualified as an epistemological ‘anti-realist', since he never maintained that the aim of science is just that of finding theories that are simply ‘empirically adequate', to put it in the terms of the contemporary debate.
The Galilean and Newtonian views of science remained paradigmatic for the development of natural science until the end of the 19th century, with an increasing favor accorded to realism, both ontological and epistemological. This could happen because mechanics quickly became the provider of a minimal metaphysical ontology for natural science, by supporting either the ‘atomistic' view that the ultimate ground of things are material particles moving in empty space, or the ‘continuistic' view of a material impalpable substratum filling the whole of space in which physical actions propagate and causally produce ascertainable phenomena.
The advantage of these views was that both of them gave an intuitive ‘visualizable’ picture of physical reality and could be expressed in adequate mathematical formulations, so that each one could be considered as offering the true portrayal of reality: the disadvantage was that they were incompatible and only one could be true. For a certain while they seemed to be ‘empirically equivalent’; later on they could be considered as separately suitable for different domains of physics; finally both appeared inadequate to fully account even for the empirical phenomena investigated in the particular branch of physics where each of them had been considered suitable (viz., thermodynamics for the atomistic view, and electrodynamics for the continuistic view). This situation produced a crisis of epistemological realism because it indicated that even the most sophisticated physical theories did not succeed in being true of their intended domains. Still, both views shared the common background framework of ‘classical’ mechanics; but with the advent of quantum mechanics and relativity theory at the beginning of the 20th century even that background was challenged and anti-realism became the most favorite attitude in the philosophy of science. Ingenuous efforts of saving at least a restricted version of realism regarding not physical reality ‘in itself but the ‘objects’ of science were undertaken through a recovery of the Kantian doctrine of transcendentally founded objective knowledge of phenomena.
Nonetheless, a distrust in the genuine cognitive powers of reason in favor of an almost exclusive confidence in observation became the dominant philosophical understanding of science.The story that we have taken the liberty of roughly outlining in its most salient lines (because is well-known) seems to deprive of any plausibility the spontaneous conviction that we are in a situation of progress with respect to our ancestors because we know more and better than them. For, if we try to explain why we are in such a more advanced cognitive situation, it is inevitable that we refer to the advancements of knowledge realized in the different sciences. The same conviction is expressed, by the way, in the often repeated statement that the knowledge attained by the different sciences in their respective fields during the last hundred years is greater than the knowledge accumulated during the entire history of human kind. To see that this is not just a naive impression of common sense it is sufficient to remember that such a respected philosopher as Wilfrid Sellars has thematically contrasted the “manifest image” of the world accepted by common sense with the “scientific image”, the first being wrong and the second true.[6] Without overlooking the criticisms that can be addressed to certain parts of Sellars’ doctrine, it is undeniable that its core is correct, and this because we must be able to recover the requirement of truth for scientific theories as something that is not reducible to the generic requirement of objectivity but is rather strictly related with a better understanding of the concept of objectivity itself. This in particular requires overcoming the ‘strict empiricist’ position that has inspired the main-stream philosophy of science of a good portion of the 20th century, in order to give back to reason its legitimate credentials in the progress of scientific knowledge, and it is not by chance that the renewed favor for realism that has been occurring in the last few decades often rehabilitates the notion of truth for scientific theories that seemed out of place regarding science especially within the analytic philosophy of science of the first half of the 20th century.
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