Philosophy of science
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Philosophy of science is the part of philosophy that studies sciences. Philosophers who are interested in philosophy of science try to explain how a human knowledge, that means all that we are able to understand, could be a science (by induction and observation, by deduction, or by an other method ?), what kind of explanation is science and what exactly science could teach us about nature and universe.
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[change] What is mean by the word “science” ?
[change] Popular ideas about science
The word “science” is used in everyday life language in a lot of domains that don't seem to concern directly philosophy of science.[1] For example, when one says that science proves something, one means that this thing is absolutely true. Advertising uses so the word “science” to give to some object more value, because one believes that if science says that a product has a certain property, then it must have this property.
More generally, science is conceived like something as a knowledge about the world that we must believe. And we think usually that such a belief is right because scientifical truths are proved by direct observation of the facts. In this view, a scientist simply describes what he observes by the means of his senses, that is to say, what he can observe in experience.
[change] A “naive” conception of science
For the common sense[2], then, science begins with observations : all scientifical knowledges come from the facts of experience, and theories are produced by the observation of this facts and could then be tested by prediction.
Here is a schema of this idea of science that some philosophers call a naive conception of science[3] :
---> INDUCTION -----> LAWS AND THEORIES -----> DEDUCTION --->
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FACTS OF EXPERIENCE PREDICTIONS AND EXPLANATIONS
Although the majority of philosophers don't think that this conception could be true, it shows to us the essential notions of philosophy of science : fact, induction, law, and so on. The aim of the philosophy of science is to understand what we really mean by those notions and how we could define them for justify the scientifical knowledge.
[change] Scientifical laws
[change] Universal laws
All men can observe, in everyday life, that there is some regularities in the world, or, in others words, that there is some facts that are always linked to some others facts that are always the same[4] ; for example :
- day follows night ;
- fire is hot.
If such a regularity is observed at all times and all places, it is then expressed in a form called universal law. A universal law says to us that when something is, at any times and any places, then an another thing must be. For example, if fire is hot is an universal law, when there is (or was or will be) fire in a place of the universe, it's absolutely certain that, in all cases, fire is hot.
For express in a simple and clear way the form of this kind of regularities that are universel, symbolic expressions are used :
- (x) (Px ⊃ Qx)
In this logical expression, (x) means all x, that is to say, in any case where there is a x. x itself is what is called a variable, that is to say, that it can refer to a lot of things, for example, some material body. Px means that x is P or has the property P, and Qx means that x is Q or has the property Q. The symbol ⊃ links Px to Qx, and corresponds to the English if... then... We can then read the expression (Px ⊃ Qx) in this way : if x is P, then x is also Q.
Rudolf Carnap[5] gives the following illutration for understand this logical expression : For every body x, if that body is heated, that body will expand. This illustration is the law of thermal expansion. Of course, this sentence is a very simplified formulation of this law.
A universal law can then be describe as a law that says that if there is a x, and if x is P (or has the property P), then x is Q (or has the property Q). Such a description is the simplest one, but doesn't describe all kind of scientific laws.
[change] Statistical laws
In a lot of cases, it is not possible to say that if x is P, then, at all times and all places, x is Q ; it is only possible to say that, sometimes, when x is P then x is Q. For example, each child is a boy or a girl ; in this case, there is no universel law, because if x is a child, an universal law can't say to us that it is a boy ; in other words, it is not the case that a child must be necessarly (or in all cases) a boy (or a girl). We can formalise this example in this way :
- (x) (Px ⊃ (
))
The symbol 
is a exclusive disjunction, and, in this example, it means that x is Q is true or x is R is true, but when x is Q is true, x is R is false, and when x is R is true, x is Q is false. We know that one or the other must be true, but we don't able to determine simply by the means of a universal law which of them is true and which of them is false.
However, even in such a case, a kind of law is sometimes possible. Indeed, by counting boys and girls, we know that about half of the children born each year are girls. Therefore, there is a measure of the fact that each child is a boy or a girl, and this measure is a law that is called a statistical law.
What teachs us exactly a statitical law ? It teachs us that a fact happens a certain number of times, what is called a frequency, and it defines the probability that the fact happens. Therefore, if x is a child, if we don't know if this child is a boy or a girl, however we know that half a time a child is a boy.
[change] Facts and laws
When we know an universal or a statistical law, we think that we have some knowlegde about objects of the world. Both kind of laws learn us something about what is called facts. A fact is a singular thing or a singular event ; for example, this morning, the sun rose is a fact, and we can express this fact by a sentence. When we know a fact, we have only the knowledge of this fact in this singularity, and therefore such a sentence don't tell us why that is so.
By contrast, if we know why day follows night, we express it by laws. Therefore, scientifical laws are explanations about facts, and, by the means of those explanations, we can predict some new facts or some repetitions of a fact. It can be formalised in this way :
- (x) (Px ⊃ Qx)
- Pa
- Qa
1 is the universal law we want to apply to a. a is a particular object.
2 means that a has the property P : for example, we have observe that a is P.
3 is the deduction that logically follows 1 and 2 : if a has the property P (2), then a has the property Q (3). Therefore, if we know 1 (the law that explains some facts) and 2 (a fact that corresponds to Px), we can predict 3 (a new fact) and explain it by 1.
[change] The problem of induction
Scientifical laws allow men to discover and predict new facts. But a more fondamental question, for philosophers and for scientists, is to understand how we can generalize our observations, and if this kind of generalisations that we call laws are really valides.
As we have seen, for the naive conception of science, laws come directly from facts of experience. If we observe a lot of times a fact A in various situations, and if we observe that all A we have seen have the property B, then we could conclude that all A must have the property B. This is the basic formulation of the principle of induction.[6]
[change] Notes
[change] Bibliography
- CARNAP, Rudolf, An Introduction to the Philosophy of Science (the first chapters are written in a very simple way), Dover Publications; New Ed edition, January 17, 1995, ISBN 0-486-28318-6
- CHALMERS, Alan F., What is this thing called science ? An assesment of the nature and status of science and its methods, 1976, 1982, 1999, Open University Press, ISBN 0-335-20109-1
[change] See also
[change] Philosophy of science
- Epistemology
- Philosophy of physics
[change] Notions
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