A brief tour of Rationalism

By Massimo Pigliucci www.loveofwisdom.org

Many meanings

• 17 th and 18 th 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 necessary truths. , philosophy can uncover

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.

The father of modern philosophy: Renée Descartes

• The method of radical doubt.

• The only thing we can know: • Our weapon: seeing things clearly and distinctly under the ‘light of nature.’ cogito ergo sum .

natural light proves guarantees existence of God

Two problems for Descartes

1. The Cartesian circle: natural light proves guarantees existence of God 2. The Cartesian trade-off: more interesting purely rational truths more certain empirical knowledge

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?)

Leibniz: the best of all possible worlds

A fundamental distinction: truths of reason vs. truths of fact logically necessary the sum of the angles in a triangle is 180º contingent Julius Caesar crossed the Rubicon

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…)

The empiricist critique: Locke, the mind is a

tabula rasa

Innatism is untenable because the universality of certain human ideas proves nothing: a. “White is not black” is universal, but ‘white’ and ‘black’ are derived from experience.

b. Many human beings seem to be unaware of many alleged universals.

Everything comes from experience The philosophical program of rationalism is flawed.

Hume’s fork Like Leibniz, distinguishes two objects of human reason Relations of ideas Discoverable by thought alone, true with certainty (but tautologous) Matters of fact Require experience, always possibly wrong Hume’s fork

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 don’t actually observe necessity, all we have is correlations.

Problems with Hume’s account: we don’t actually automatically infer causality from repeated association; when multiple causes are at work, there is no necessary connection (e.g., smoking and cancer).

The Kantian synthesis: four kinds of judgment A priori = ?

Analytic A posteriori = ?

Synthetic

The possibility of synthetic a priori judgments A priori A posteriori Analytic Synthetic Examples: mathematical propositions, law of causation

Kant and the limits of reason Phenomena The world as we observe it, mediated by perception Noumena The world as it is in itself Rationalists want this, but they have to contend themselves with this.

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

Hegel and dialectics Hegel’s model of human understanding (and of history): Synthesis 2 (and Thesis 3) Antithesis 2 Synthesis 1 (and Thesis 2) Thesis 1 (based on sense impressions) Antithesis 1

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 statements are not pictures of facts in the world they are literally meaningless.

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

Quine’s attack on the two dogmas of empiricism Against dogma 1: there is no hard distinction between facts and values.

>> Empiricism cannot be completely objective.

Against dogma 2: the significance and truth of propositions cannot be established in isolation.

>> Empiricism needs assumptions.

A shift in the model A priori & Analytic A posteriori & Synthetic closer to analytic experience closer to synthetic

Massimo: Picture of Chomsky?

Chomsky and the revival of innatism 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.

Too few data are presented to the child Too many combinations of words are generated Modern neurobiology has identified parts of the brain that recognize specific aspects of language

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).

Hume’s 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 them —A Treatise of Human Nature

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)

Massimo: Pictures of Feye and Rorty?

The all-out attack against rationalism (

sensu lato

): relativism • 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.