allzermalmer

Truth suffers from too much analysis

Posts Tagged ‘Refutability’

Did Popper Solve The Problem of Induction?

Posted by allzermalmer on October 3, 2012

Karl Popper said that he believed he had solved the “Problem of Induction”, or what he called “Hume’s Problem”. But did Karl Popper really solve the Problem of Induction or Hume’s Problem? Maybe we should (1) take a look at what Popper considered to be Hume’s problem, and (2) see what Popper says his solution to the problem is. (Whether or not Popper did correctly identify Hume’s problem, is of no concern here).

Before we do this, I think we should start out with something basic, or part of basic, logic.

(A) Universal Quantifier Affirmative (All S are P): For each x, if x is S, then x is P
(E) Universal Quantifier Negation (No S are P) : For each x, if x is S, then x is not P
(I) Existential Quantifier Affirmative (Some S are P): There exists at least one x, such that x is S and x is P
(O) Existential Quantifier Negation (Some S are not P): There exists at least one x, such that x is S and x is not P

“All of the categorical propositions illustrated above can be expressed by using either the universal quantifier alone or the existential quantifier alone. Actually, what this amounts to is the definition of the universal quantification of propositions in terms of existential quantification and the definition of existential propositions in terms of universal quantification.” p. 349 Formal Logic: An Introductory Textbook by John Arthur Mourant

Now this means that the Universal Quantifier (UQ) can be expressed in a logically equivalent form to an Existential Quantifier (EQ), and the Existential Quantifier can be expressed in a logically equivalent form to Universal Quantifier. For something to be logically equivalent means they mean the same thing in a logical sense. Logically equivalent statements have the exact same truth. One can’t be true and the other false, for this would mean they are both necessarily false.

Universal Quantifiers to Existential Quantifiers

A: For each x, if x is S, then x is P    There does not exist at least one x, such that x is S and x is not P
E: For each x, if x is S, then x is not P    There does not exist at least one x, such that x is S and x is P
I: Not for each x, if x is S, then x is not P    There exists at least one x, such that x is S and x is P
O: Not for each x, if x is S, then x is P   There exists at least one x, such that x is S and x is not P

A: For each x, if x is Crow, then x is Black  ↔  There does not exist at least one x, such that x is Crow and x is not Black
E: For each x, if x is Crow, then x is not Black  ↔  There does not exist at least one x, such that x is Crow and x is Black
I: Not for each x, if x is Crow, then x is not Black  ↔  There exists at least on x, such that x is Crow and x is Black
O: Not for each x, if x is Crow, then x is Black  ↔  There exists at least on x, such that x is Crow and x is not Black

Existential Quantifiers to Universal Quantifiers

A: There does not exist at least one x, such that x is S and x is not P    For each x, if x is S, then x is P
E: There does not exist at least one x, such that x is S and x is P     For each x, if x is S, then x is not P
I: There exists at least one x, such that x is S and x is P   Not for each x, if x is S, then x is not P
O: There exists at least one x, such that x is S and x is not P    Not for each x, if x is S, then x is P

A: There does not exist at least one x, such that x is Crow and x is not Black  ↔  For each x, if x is Crow, then x is Black
E:
There does not exist at least one x, such that x is S and x is P  ↔  For each x, if x is Crow, then x is not Black 
I:
There exists at least one x, such that x is Crow and x is Black  ↔  Not for each x, if x is Crow, then x is not Black
O:
There exists at least one x, such that x is Crow and x is not Black  ↔  Not for each x, if x is Crow, then x is Black

It needs to be pointed out first that there are two types of statements.
(1)Necessary Truth: Statement whose denial is self-contradictory.
(2) Contingent Truth: One that logically (that is, without self-contradiction) could have been either true or false.

(1a) “All bachelors are unmarried males”
(2a) “Justin Bieber is an unmarried male”

A necessary truth is said to have no empirical content. A contingent truth is said to have empirical content.

Hume’s problem was that he found that he cannot justify induction by demonstrative argument, since he can always imagine a different conclusion.

What Popper takes to be “Hume’s Problem”

“It is usual to call an inference ‘inductive’ if it passes from singular statements (sometimes called ‘particular’ statements), such as accounts of the results of observations or experiments, to universal statements, such as hypotheses or theories. Now it is far from obvious, from a logical point of view, that we are justified in inferring universal statements from singular ones, no matter how numerous; for any conclusions drawn in this way may always turn out to be false: no matter how many instances of white swans we may have observed, this does not justify the conclusion that all swans are white. The question whether inductive inferences are justified, or under what conditions, is known as the problem of induction.” pg. 3-4 Logic of Scientific Discovery

“The root of this problem [of induction] is the apparent contradiction between what may be called ‘the fundamental thesis of empiricism’- the thesis that experience alone can decide upon the truth or falsity of scientific statements- and Hume’s realization of the inadmissibility of inductive arguments.” pg. 20 Logic of Scientific Discovery

Here’s an Inductive argument

Singular: (P1) There exists at least one x, such that x is Crow and x is Black
Singular: (P2) There exists at least one x, such that x is Crow and x is Black

Universal: (C) For each x, if x is Crow, then x is Black

Popper’s Solution to “Hume’s Problem”

“Consequently it is possible by means of purely deductive inferences (with the help of the modus tollens of classical logic) to argue from the truth of singular statements to the falsity of universal statements. Such an argument to the falsity of universal statements is the only strictly deductive kind of inference that proceeds, as it were, in the ‘inductive direction’ that is, from singular to universal statements.”pg. 21 Logic of Scientific Discovery

Here’s Popper’s solution

Universal: (P1) For each x, if x is Crow, then x is not Black
Singular: (P2) There exists at least one x, such that x is Crow and x is Black
Universal: (C) Not for each x, if x is Crow, then x is not Black

Singular statement leads to a universal statement. From there exists at least one x, such that x is Crow and x is Black, the conclusion is reached that not for each x, if x is Crow, then x is not Black.

Here’s Poppers understanding of Induction: “It…passes from singular statements…to universal statements…”

Here’s Poppers solution to the ‘Problem of Induction: “Such an argument to the falsity of universal statements is… from singular to universal statements.”

So going from singular statement to universal statement can be justified by  going from singular statements to universal statements. This falls for the problem of induction again, because this is a circular argument that is used to defend induction.

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Popper, Hume, Induction, Falsifiability, and Science

Posted by allzermalmer on September 30, 2012

Here are some interesting things from Karl Popper on Falsification and Induction, or Hume on Induction.

“we merely have to realize that our ‘adoption’ of scientific theories can only be tentative; that they always are and will remain guesses or conjectures or hypotheses. They are put forward, of course, in the hope of hitting upon the truth, even though they miss it more often than not. They may be true or false. They may be tested by observation (it is the main task of science to make these tests more and more severe), and rejected if they do not pass…Indeed, we can do no more with a proposed law than test it: it is no use pretending that we have established universal theories, or justified them, or made them probably, by observation. We just have not done so, and cannot do so. We cannot give any positive reasons for them. They remain guesses or conjectures- though well tested ones.” Realism and the Aim of Science

Now someone might wonder how we cannot give any positive reasons for establishing the universal theories, or justified them, or made them probable, by all the observations that confirm its predictions on tests. This comes from what Popper takes to be Hume’s problem of induction.

“[Hume] tried to show that any inductive inference- any reasoning from singular and observable cases (and their repeated occurrence) to anything like regularities or laws- must be invalid. Any such inference, he tried to show, could not een be approximately or partially valid. It could not even be a probable inference: it must, rather, be completely baseless, and must always remain so, however great the number of the observed instances might be. Thus he tried to show that we cannot validly reason from the known to the unknown, or from what has been experienced to what has not been experienced (and thus, for example, from the past to the future): no matter how often the sun has been observed regularly to rise and set, even the greatest number of observed instances does not constitute what I have called a positive reason for the regularity, or the law, of the sun’s rising and setting. Thus it can neither establish this law nor make it probable.” Realism and the Aim of Science

I think it should be pointed out, Hume did bring up that the basic idea of induction was that “we suppose, but are never able to prove, that there must be a resemblance betwixt those objects, of which we have had experience, and those which lie beyond the reach of our discovery.” Induction is also done in other ways besides going from particular statements to universal statements.

[I.] Move form particular statement to particular statement.
In 1997 the Chicago Bulls beat the Utah Jazz in the NBA Finals. In 1998 the Chicago Bulls beat the Utah Jazz in the NBA Finals. Thus, the Chicago Bulls will win against the Utah Jazz the next time they play in the NBA Finals.

[II.] Move from general statement to general statement.
All NFL teams made tons of money this year. Thus, all NFL teams will make tons of money next year.

[III.] Move from general statement to particular statement.
All NFL teams made tons of money this year. Thus, the Ravens will make tons of money next year.

[IV.] Move from particular statement to general statement.
This crow is black. Thus, all crows are black.

Each of these, though, follow what Hume points out for Induction. They are going from the known to the unknown, which does not have to include the future or past.Hume also says that the only thing that can take us from the known to the unknown is causality, or a necessary connection between two events to form a necessary causal relation. But Hume already pointed out that this relation is not found by experience. So Hume comes to the conclusion that since the necessary relation between cause and effect or continuation of that relationship, is not shown by experience nor demonstrative,  or that the principle of induction is not known by experience or demonstrative, but that they are creations of the human imagination that cannot be shown to be true based on experience or reason, and any justification of them will either rely on an infinite regress or circular reasoning. So they cannot be proven to be true.

This would mean that when science proposes either a causal connection, or what will happen in the future, or what happens beneath sensible qualities, cannot be proved by experience to be true , or by reason to be true, or even held to be probably true. IOW, we are not justified in proposing things beyond what is known, since they cannot be shown to be true or probably true. So scientific hypotheses are unjustified and cannot be shown to be true or probably true, or natural laws cannot be shown to be true or probably true or justified.

Popper comes along and tries to save science, in some way. But you notice where his position eventually leads as well. He admits with Hume that we cannot demonstrate the truth of a scientific hypothesis or explanation; we cannot show by experiment the truth of a scientific hypothesis or explanation; we cannot show that a scientific hypothesis or explanation is probably true. All we can do is show if they are false. We can give negative reasons to a scientific hypothesis or explanation by it failing its severe experimental/observational tests. This is because it follows the demonstrative inference of modus tollens and disjunctive syllogism, so we can demonstrate that a scientific hypothesis or explanation is false.

So falsifiability, or refutabilty, can show you only that a scientific hypothesis or explanation is false. Refutability cannot demonstrate that the hypothesis or explanation is true, or has been shown by experience to be true, or is probably true.  It can only tell you that it may be true, and it has not failed any of its tests so far. It doesn’t even appears to care if something is true, only that it can be shown to be false.

And here are Hume on what Induction is, or relies on.

“that which we have had no experience, must resemble those which we have had experience, and nature continues uniformly the same.” Treatise of Human Nature:  Book I (Of the Understanding), Part III (Of Knowledge & Probability), Sect.VI.Of the Inference from the Impression to the Idea

“probability is founded on the presumpition of a resemblances betweixt those objects, of which we have had experience, and those, of which we have had none…” Treatise of Human Nature:  Book I (Of the Understanding), Part III (Of Knowledge & Probability), Sect.VI.Of the Inference from the Impression to the Idea

“Thus not only our reason fails us in the discovery of the ultimate connexion of causes and effects, but even after experience has informed us of their constant conjunction, it is impossible for us to satisfy ourselves by our reason, why we should extend that experience beyond those particular instances, which have fallen under our observation. We suppose, but are never able to prove, that there must be a resemblance betwixt those objects, of which we have had experience, and those which lie beyond the reach of our discovery.” Treatise of Human Nature:  Book I (Of the Understanding), Part III (Of Knowledge & Probability), Sect.VI.Of the Inference from the Impression to the Idea

“we always presume, when we see like sensible qualities, that they have like secret powers, and expect that effects, similar to those which we have experienced, will follow from them.” An Enquiry Concerning Human Understanding: Section IV. Sceptical Doubts Concerning the Operations of the Understanding, Part II

“all arguments from experience are founded on the similarity which we discover among natural objects, and by which we are induced to expect effects similar to those which we have found to follow from such objects.” An Enquiry Concerning Human Understanding: Section IV. Sceptical Doubts Concerning the Operations of the Understanding, Part II

“From causes which appear similar we expect similar effects. This is the sum of all our experimental conclusions.” An Enquiry Concerning Human Understanding: Section IV. Sceptical Doubts Concerning the Operations of the Understanding, Part II

 

 

 

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