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A brief tour of Rationalism

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Title: A brief tour of Rationalism


1
A brief tour of Rationalism
By Massimo Pigliucci
www.loveofwisdom.org
2
Many meanings
  • 17th and 18th centuries freethinking,
    atheism (as in J. S. Mill).
  • Generic belief in the importance of reason
    to settle questions about truth (every
    philosopher).
  • Technical a cluster concept including
  • Innatism, possibility of innate knowledge
  • Apriorism, knowledge without the senses
  • Necessitarianism, philosophy can
    uncover necessary truths.

3
The first rationalist Plato
  • Theory of forms reality is a pale reflection
    of the forms (simile of the cave).
  • Importance of mathematics and geometry.
  • Innate knowledge the theory of recollection.
  • Philosophy is concerned with what must be, not
    merely with what happens to be.

4
The father of modern philosophy Renée Descartes
  • The method of radical doubt.
  • The only thing we can know cogito ergo sum.
  • Our weapon seeing things clearly and
    distinctly under the light of nature.

proves
natural light
existence of God
guarantees
5
Two problems for Descartes
1. The Cartesian circle
proves
natural light
existence of God
guarantees
2. The Cartesian trade-off
more interesting
empirical knowledge
purely rational truths
more certain
6
Spinoza all the universe is one (monism)
  • Truths about the universe can be derived
    entirely in a deductive fashion.
  • How many substances?
  • Aristotle Scholastics many
  • Descartes two (mind and body)
  • Spinoza necessarily one (God-nature).
  • How do we know that a theory is true?
  • Correspondence with reality. Not for Spinoza.
  • Internal coherence. Bingo! (But many truths?)

7
Leibniz the best of all possible worlds
A fundamental distinction truths of reason vs.
truths of fact
contingent
logically necessary
Julius Caesar crossed the Rubicon
the sum of the angles in a triangle is 180º
8
Substances and monads
  • Many substances (back to Aristotle).
  • Individual units (monads) are independent and
    complete.

If the monads are independent, how do causal
interactions occur?
If the monads are complete, how do we get
contingency and free will?
God created the best of all possible worlds (Dr.
Pangloss)
9
The empiricist critique Locke, the mind is a
tabula rasa
  • Innatism is untenable because the universality of
    certain human ideas proves nothing
  • White is not black is universal, but
    white and black are derived from experience.
  • Many human beings seem to be unaware of many
    alleged universals.

The philosophical program of rationalism is
flawed.
Everything comes from experience
10
Humes fork
Like Leibniz, distinguishes two objects of human
reason
Relations of ideas
Matters of fact
Discoverable by thought alone, true with
certainty (but tautologous)
Require experience, always possibly wrong
Humes fork
11
Hume on causality
  • Our perception of causality depends on
  • Priority (A comes before B)
  • Contiguity (A happens near B)
  • Necessary connection (A is necessary for B to
    happen).

BUT, we dont actually observe necessity, all we
have is correlations.
Problems with Humes account we dont
actually automatically infer causality from
repeated association when multiple causes are
at work, there is no necessary connection (e.g.,
smoking and cancer).
12
The Kantian synthesis four kinds of judgment
?
Analytic
A priori
How judgment is reached
What they tell us about the world
?
A posteriori
Synthetic
13
The possibility of synthetic a priori judgments
A priori
Analytic
Synthetic
A posteriori
Examples mathematical propositions, law of
causation
14
Kant and the limits of reason
Phenomena Noumena
The world as we observe it, mediated by
perception
The world as it is in itself
Rationalists want this, but they have to
contend themselves with this.
15
Kant on understanding and causality
The mind interprets the world using
certain fundamental concepts (categories), which
are a priori notions, such as substance and
causality.
experience
The reconciliation Thoughts without content are
empty intuitions without concepts are blind.
a priori categories
16
Hegel and dialectics
Hegels model of human understanding (and of
history)
Synthesis 2 (and Thesis 3)
Antithesis 2
Synthesis 1 (and Thesis 2)
Antithesis 1
Thesis 1 (based on sense impressions)
17
The rise and fall of logical positivism
  • The precursors
  • Russell, even theoretical entities such as
    atoms are arrived at by the logical construction
    of sense-data.
  • Early Wittgenstein, since metaphysical statement
    s are not pictures of facts in the world they
    are literally meaningless.

18
Doing away with metaphysics?
Verification principle only statements that
can be verified empirically are meaningful.
While mathematics seems an exception, it really
is reducible to a series of tautologies.
Problems
The verification principle is not verifiable
empirically
Some products of science are either
unobservable or smell of metaphysics
19
Quines attack on the two dogmas of empiricism
Against dogma 1 there is no hard
distinction between facts and values. gtgt
Empiricism cannot be completely
objective. Against dogma 2 the significance and
truth of propositions cannot be established in
isolation. gtgt Empiricism needs assumptions.
20
A shift in the model

A priori
Analytic
Synthetic
A posteriori

closer to analytic
experience
closer to synthetic
21
Chomsky and the revival of innatism
Massimo Picture of Chomsky?
Skinner and behaviorism language is acquired
by continuous stimulus / response. Chomsky we
have an innate ability to fit the specifics of a
language into a universal grammar.
Modern neurobiology has identified parts of the
brain that recognize specific aspects of language
Too few data are presented to the child
Too many combinations of words are generated
22
Rationalism in ethics
  • For rationalists, ethics can be
  • Objective (moral properties are out there)
  • Necessary (moral truths are unalterable)
  • A priori (one understands moral
    principles without any priori experience).

23
Humes critique of rational ethics
  1. Objectivism? Ethical judgments is a matter
    of feelings of disapprobation
  2. Necessity? Moral truths cannot be expressed in
    terms equivalent to mathematics or logic
  3. A priori knowledge? One has to feel the
    emotions, it cannot derive them by reasoning.

Reason is and ought only to be the slave of the
passions, and can never pretend to any other
office than to serve and obey themA Treatise of
Human Nature
24
Karl Popper, induction and deduction
  • Hume introduced the problem of induction.
  • Popper proposed that science does not
    proceed by induction at all, but by deduction
    through falsification

If T then O not (O), therefore not(T) (modus
tollens)
25
The all-out attack against rationalism (sensu
lato) relativism
Massimo Pictures of Feye and Rorty?
  • Feyerabend Western science is simply
    a dominant ideology, one tradition among many.
  • Rorty there is no such thing as
    philosophical knowledge, objectivity does not
    exist.
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