(November 3, 2011)
1. Deductive vs Inductive reasoning
a) Deductive reasoning:
All Greeks are mortal
Socrates is a Greek
Therefore, Socrates is mortal.
b) Inductive reasoning:
This raven is black.
That raven is black.
That other raven is black.
That further raven over there is black.
Therefore, all ravens are black.
A kind of reasoning that constructs or evaluates propositions that are
abstractions of observations.
form of reasoning that makes generalizations based on individual instances
2. The "Problem" of Induction
Scientific reasoning is, for the most part, inductive reasoning
We think of science as, par excellence the instrument of knowledge and certainly
The laws of nature are not relations of idea thy are matters of fact
We have no good reason to believe:
o That the law of gravity will hold tomorrow
o That the sun will rise tomorrow
In general: that the future will resemble the past in these respects
Or rather… that unobserved portions of the universe resemble observed portions of the
universe, in these respects
In other words
Hume’s view is that inductive reasoning is simply a habit:
o We get used to the sum of rising every morning, so we assume it always will
What reason is there to think that the future will resemble the past?
To search for such a reason of
3. First Solution: The Inductive Principle: "the future will resemble the past"
Maybe we could find a principle, call it the “inductive principle” that we could insert into
Inductive Argument so that they become Deductive Argument
The Inductive Principle would be something like: the future
Ex. This raven is black, that raven is black- the future will resemble the past (inductive
argument) therefore, all ravens are black
Future will resemble the past, we are relying on the past
The inductive principle itself relies on an inductive argument (we’re reasoning in a
circle) Problem with this solution: circular argument
4. Second Solution: The Pragmatic Solution (à la Pascal's Wager)
Hans Reichenback (1891-1953) American Philosopher
Reichenback proposed a pragmatic solution to the classical problem of induction, a
solution that takes its inspiration from Pascal’s Wager
We could set it up this way:
Where L stands