sábado, 31 de marzo de 2007

Hempel’s General Ideas On Philosophy Of Science

Confirmation

The paradox of confirmation of the raven involves the confirmation of the generalization “all ravens are black” by an observation of something that satisfies the logical equivalent statement “all non-black things are non-ravens”, like a red apple, or a white handkerchief . These consequences are paradoxical, but Hempel argues, they must be accepted as valid. My point is that even something satisfies the two conditions non-black non raven it isn’t a confirmation of the generalization “all ravens are black”, a fact may be consistent with the hypothesis or even be an instance of it, without being evidence for it.

Degree Of Confirmation

This concept reflects the assumption which might be called the statistical version of the principle of induction and implies that the relative frequencies observed in the ‘past’ will remain fairly stable in the ‘future’. What degree of confirmation shall be assigned to H on the basis of E? And is represented such as ‘dc (H, E)‘. If a fixed frequency distribution ∆ is given or hypothetically assumed, then it is possible to define the concept pr ( H, E, ∆ ) the probability of H relatively to E according to the distribution ∆, defining dc (H, E)= pr ( H, E, ∆ ). This is an empirical reconstruction of the concept of degree of confirmation On the basis of a given Evidence, we infer the optimum distribution ∆ and then assign to H, as its degree of confirmation the probability which H possesses relatively to E according to ∆ .

Science doesn’t aim al high probabilities, it aims at a high informative content, based on experience, a hypothesis may be very probable because it may tell us very little, a high degree of probability is not an indication of a confirmation it may be only low informative content. Other point in contrast with this confirmation view is that it's based almost exclusively on frequencies of observations, this leaves out many other considerations, such as the previous knowledge on the subject, and its role in confirming the hypothesis.

Hempel on Theories

Hempel defined a theory as :”a coherent, integrated set of statements containing: (1) internal principles, (2) bridge principles, and (3) an identifiable body of phenomena to be explained”

First we have a understood vocabulary, according to the phenomena we’ll be able to state some empirical laws We introduce a new vocabulary, the internal principles to state laws describing the phenomena. The bridge principles are introduced in order to explain our empirical laws which allow us to establish logical connections between statements cast in the vocabulary of our new theory and statements cast in our antecedently understood vocabulary.

Although I agree with Lakato’s proposal of Scientific Research Programs, these are composed of theories which are composed of principles and this arrangement that Hempel describes of theories seems appropriate and important because verisimilitude and fallibility are ideas that are applied to theories and cannot be applied to research programs, but are indeed necessary for the qualification of those into progressive or degenerating.

Scientific Explanation

To Carl Hempel, scientific explanation is an argument that offers reasons for a given phenomenon to happen. It has to satisfied three requirements: explanatory relevance, which means that the explanation “affords good grounds for believing that the phenomenon to be explained did, or does, indeed occur.” Testability, the statement explaining the phenomena must be open to empirical test, and the premises must contain a scientific law.

The set of premises that explains the phenomenon is called the explanans; the conclusion is the phenomenon to be explained and is called the explanandum, it can be a singular fact or a general law. There are two explanans subclasses; one contains sentences which state specific antecedent conditions, the other represent general laws.

Hempel’s claim is that (a) every correct scientific explanation conforms to either the Deductive-Nomological model, D/N or the Inductive-Statistical model, I/S and that (b) anything that conforms to either of these models is a correct scientific explanation . These two models have very similar conditions:

• The explanation must be a deductively valid argument in the D/N model, so that the explanans must entail the explanandum. In the I/S model, the explanandum follows from the explanans with high inductive probability.
• In the D/N model the law-like statements in the explanans state actual laws. In the I/S model the explanans must contain at least one statistical law.
• The explanans must have empirical content.
• The premises contained in the explanans must be true or highly confirmed by all the relevant evidence available.
• And in the case of the I/S model the law must be “maximally specific”.

The second condition is the one which primarily distinguish them, and is also the one which is more debatable, in the case of the DN-model laws and law-like statements are conceptions that limit the scope for explanation, and in the case of the I/S model the statistical laws seem to not be enough for a proper explanation, natural laws make an explanation more accurate instead statistical laws make explanations doubtful. Other fault in which the two models fail is that they don’t properly reflect causal connections, they leave out significant considerations about the role of causality in explanation.

Hempel believed that science evolved in a continuous manner. New theory did not contradict past theory, more comprehensive theory replaced compatible, older theory. Each successive theory's explanation was closer to the truth than the theory before. It was the truth, and the prediction and control that came with it, that was the goal of logical-empirical science. In his view of progress Hempel denies the fact that some theories that have been defeated are false, and are not included in the theories by which were defeated. I believed that science evolves making progress with respect to truth, that is discovering new facts, and making predictions, in this way I agree with Hempel’s view.