A brief tour of Rationalism

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A brief tour of Rationalism
By Massimo Pigliucci
www.loveofwisdom.org
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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.

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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.

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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
naturallight
existenceof God
guarantees
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Two problems for Descartes
1. The Cartesian circle
proves
naturallight
existenceof God
guarantees
2. The Cartesian trade-off
more interesting
empiricalknowledge
purely rationaltruths
more certain
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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?)

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Leibniz the best of allpossible worlds
A fundamental distinctiontruths of reason vs.
truths of fact
contingent
logically necessary
Julius Caesarcrossed the Rubicon
the sum of the anglesin a triangle is 180º
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Substances and monads

• Many substances (back to Aristotle).
• Individual units (monads) are independent and
  complete.

If the monads are independent, how docausal
interactions occur?
If the monads arecomplete, how do we get
contingency and free will?
God created the best of allpossible worlds (Dr.
Pangloss)
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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
  whiteand black are derived from experience.
• Many human beings seem to be unaware of many
  alleged universals.

The philosophicalprogram of rationalismis
flawed.
Everything comes from experience
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Humes fork
Like Leibniz, distinguishes two objects of human
reason
Relations of ideas
Matters of fact
Discoverable bythought alone,true with
certainty(but tautologous)
Require experience,always possibly wrong
Humes fork
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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
actuallyautomatically infer causality from
repeated association when multiple causes are
at work, there isno necessary connection (e.g.,
smoking and cancer).
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The Kantian synthesis four kinds of judgment
?
Analytic
A priori
How judgment is reached
What they tell usabout the world
?
A posteriori
Synthetic
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The possibility of synthetic a priori judgments
A priori
Analytic
Synthetic
A posteriori
Examples mathematical propositions, law of
causation
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Kant and the limits of reason
Phenomena Noumena
The world as weobserve it, mediated by
perception
The world as it isin itself
Rationalists want this,but they have to
contendthemselves with this.
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Kant on understanding and causality
The mind interprets the world using
certainfundamental concepts (categories), which
area priori notions, such as substance and
causality.
experience
The reconciliation Thoughts without contentare
empty intuitions without concepts are blind.
a priori categories
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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)
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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.

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Doing away with metaphysics?
Verification principle only statements that
canbe verified empirically are meaningful.
Whilemathematics seems an exception, it really
isreducible to a series of tautologies.
Problems
The verificationprinciple is notverifiable
empirically
Some products of scienceare either
unobservableor smell of metaphysics
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Quines attack on the two dogmas of empiricism
Against dogma 1 there is no hard
distinctionbetween facts and values. gtgt
Empiricism cannot be completely
objective. Against dogma 2 the significance and
truth ofpropositions cannot be established in
isolation. gtgt Empiricism needs assumptions.
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A shift in the model

A priori
Analytic
Synthetic
A posteriori

closer to analytic
experience
closer to synthetic
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Chomsky and the revivalof innatism
Massimo Picture of Chomsky?
Skinner and behaviorism language is acquired
bycontinuous stimulus / response.Chomsky we
have an innate ability to fit the specifics of a
language into a universal grammar.
Modern neurobiologyhas identifiedparts of the
brainthat recognize specificaspects of language
Too few dataare presentedto the child
Too manycombinationsof words aregenerated
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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).

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Humes critique of rational ethics

1. Objectivism? Ethical judgments is a matter
   offeelings 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 toserve and obey themA Treatise of
Human Nature
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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)
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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.