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**

**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**

I:

I:

**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**

O:

O:

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, touniversalstatements, 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 thatallswans are white. The question whether inductive inferences are justified, or under what conditions, is known asthe 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 tollensof 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.