For positivism, the object of scientific method is an external reality and science is signified from the observable natural phenomena. This view entails on one hand physiocracy, that is the recognition of the physio-empirical origin of knowledge and on the other hand physiocracy or objectivism, that is, the acceptance of an objective and self-sustainable existence of phenomena.
The answer to the previous arguments is constructed by the position known as underdetermination of theory from empirical indications and the theoretical weighting of the action of observation. Both these critical challenges to positivism were born out of the context of conventionalism, which historically has set the first main point of opposition to positivism (or rather, to reductionism). The basic epistemological tenet of conventionalism holds that the laws of science (such as Newtonian mechanics) and the axioms of mathematics (like Euclidian geometry) are not experimental generalizations, neither a priori knowledge but conventions or linguistic definitions. The French philosopher of science, Henri Poincare, is considered the main proponent of conventionalism.
The position of underdetermination rejects the possibility of a solely empirical determination of theory, i.e. the possibility for a theoretical schema that lies in absolute agreement with experience. The justification of the underdetermination thesis is founded on some arguments developed by Duhem and Quine and due to this it is also known as the Duhem-Quine thesis (despite that the independent views of Duhem and Quine do not always coincide).
We now come to the thesis of theory-ladenness of obseration, which also initially was put forward by Duhem. Duhem has distinctively stated the central point of this thesis in the title of a chapter of his book as ‘An Experiment in Physics is not simply the observation of a phenomenon; it is besides, the theoretical interpretation of this phenomenon.’ Later on, the thesis was adopted and developed by Kuhn, Feyerabed, Bohm, Hanson, Tulmin.
The theory-ladenness of observation, is usually understood as a two-fold concept:
a) That observations include an accompanying set of hypotheses, which appear in the form of theory of measurement, psychology of observation, linguistic orderings etc.
b) In the sense that what is regarded as a relative and precise empirical indication is based partly on the theoretical paradigm to which the empirical indication itself comes to examine.
The first concept corresponds to the thesis of underdetermination of theory. A consequence of the theory-ladenness of observation is that scientists can in principle be suspicious of a certain observation and challenge the validity of its constituent hypotheses. The second concept of they theory-ladenness of observation has some interesting consequences on the role of observation in the choice of theory. It is an obvious fact, according to this concept, that observations cannot function as objective referees in the choice of theory, when at the same time, the importance and the character of the former, and their own estimating and measuring ability is dependent upon competitive theories. It is precisely in this way that theory-laden observations can lead to opposing conclusions (in the sense of Kuhn). In addition to that, even if the supporters of different theories agree to the importance of a crucial experiment, the evident assumption would be that the different theoretical priorities of scientists would differentiate the nature of their own estimation and also the mediums used to reach this estimation. We therefore see that the thesis of the theory-ladenness of observations creates the preconditions for the existence of different scientific priorities. And it is within the intentions of social studies of science, the sociological analysis of these differences in the framework of certain scientific practices.
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