The term positivism is derived from August Comte . Because of his critical work, however, Hume can be considered the first great positivist. He showed the impossibility of deductive reasoning producing factual assertions, since deduction takes place and affects a second level, that of concepts.

Positivism and Logical Empiricism

The development of the term positivism has, however, been incessant. The basic statements of positivism are:

1) That all knowledge of the facts is based on “positive” data from experience . -that reality exists, the opposite belief is called solipsism-.

2) That beyond the realm of facts are logic and pure mathematics , recognized by Scottish empiricism and especially by Hume as belonging to “the relation of ideas”.

In a later stage of positivism the sciences thus defined acquire a purely formal character.

Mach (1838-1916)

It states that all factual knowledge consists of the conceptual organization and the elaboration of the data of immediate experience. Theories and theoretical conceptions are only instruments of prediction.

Moreover, theories can change, while the facts of observation maintain empirical regularities and constitute a firm (immutable) ground for scientific reasoning to take root. The positivist philosophers radicalized the empiricist anti-intellectualism, maintaining a radical utilitarian vision of the theories.

Avenarius (1843-1896)

He developed a biologically oriented theory of knowledge that influenced much of American pragmatism. Just as adaptation needs develop organs in organisms -Lamarckism-, so knowledge develops theories for predicting future conditions.

The concept of cause is explained in terms of the regularity observed in the sequence of events, or as a functional dependency between the observable variables. Causal relationships are not logically necessary, they are only contingent and determined by observation and especially by experimentation and inductive generalization -Hume-.

Many scientists of the 20th century, following the path opened up by Mach, to which was added the influence of some ‘philosophers of mathematics’ such as Whithead, Russell, Wittgenstein, Frege, etc, were more or less unanimously united around the positivist problem of the legitimacy of scientific theories.

Russell says, “Either we know something independently of experience, or science is a chimera.

Some philosophers of science, known as the group of the Vienna Circle, established the principles of logical empiricism:

1.Firstly they believed that the logical structure of some sciences could be specified without taking into account their contents .

2.Secondly they established the principle of verifiability , according to which the meaning of a proposition must be established through experience and observation. In this way ethics, metaphysics, religion and aesthetics were left out of any scientific consideration.

3.Thirdly, proposed a unified doctrine of science , considering that there were no fundamental differences between physics and biological sciences, or between natural and social sciences. The Vienna Circle reached its peak of activity during the period before the Second World War.

Conventionalists

Another group of inductivists, of different orientation – among them those of influence Marxist , known as Frankfurt School – are the Conventionalists , which argue that the main discoveries of science are, fundamentally, inventions of new and simpler classification systems.

The fundamental features of classical conventionalism -Poincaré- are, therefore, decisiveness and simplicity. They are also, of course, anti-realistic. In terms of Karl Popper (1959, pg. 79):

“The source of conventionalist philosophy seems to be astonishment at the austere and beautiful simplicity of the world as revealed in the laws of physics. The conventionalists (…) treat this simplicity as our own creation… (Nature is not simple), only the “laws of Nature” are simple; and these, the conventionalists maintain, are our creations and inventions, our arbitrary decisions and conventions”.

Wittgenstein and Popper

This form of logical empiricism was soon opposed by other forms of thought: Wittgenstein , also a positivist, is, however, confronted with the verificationist positions of the Vienna Circle.

Wittgenstein maintains that verification is useless. What language can communicate “shows” it, is an image of the world. For the logical positivism inherited from Wittgenstein, logical formulas say nothing about the meanings of the propositions, but limit themselves to showing the connection between the meanings of the propositions.

The fundamental answer will come from the falsification theory of Popper , which sustains the impossibility of an inductive probability with the following argument:

“In a universe containing an infinite amount of distinguishable things or space-time regions, the probability of any universal (non-tautological) law will be zero. This means that with the increase of content of a statement its probability decreases, and vice versa. (+ content = – probability).

To solve this dilemma he proposes that one should try to falsify the theory, seeking the demonstration of refutation or counter-example. In addition, he proposes a purely deductivist methodology, in reality negative or false hypothetical-deductive.

As a reaction to this approach, a number of theorists who criticize logical positivism emerge -Kuhn, Toulmin, Lakatos and even Feyerabendid-, although they differ about the nature of rationality exhibited by scientific change. They defend notions such as scientific revolution, as opposed to progress -Kuhn-, or the intervention of irrational processes in science -Feyerabend’s anarchist approach.

Popper’s heirs are now agglutinating under the Critical Rationalism , in a last effort to save science, theory and the notion of “scientific progress”, which they do not do without some difficulty, proposing as alternatives, among others, the establishment of rival Research Programs, defined by their heuristics, and that compete with each other.

The difficulties of logic models applied to the methodology of Science could therefore be summarised as follows:

The induction of the theory, from particular data, was clearly no longer justified. A deductive theory will achieve nothing because there are no sure general principles from which deduction can be derived. A false vision is inadequate because it does not reflect scientific practice – scientists do not operate in this way, abandoning theories, when they present anomalies.

The result seems to be a generalized skepticism regarding the possibility of distinguishing between valid theories and ad hoc theories, so that one usually ends up appealing to history, that is, to the passage of time as the only sure method, or at least with certain guarantees, to judge the adequacy of the models -another form of conventionalism.