Rationalism

Rationalism and Empiricism, 1

Empiricism: All knowledge of the world comes from experience

Rationalism: Some knowledge of the world is independent of experience— that is, some knowledge is inborn (innate)

Trifling Propositions Locke: trifling

propositions are Identical propositions

(Logical truths): “A soul is a soul”, “Lead is lead”

Truths by definition: predicate is part of subject, e.g., “Lead is a metal”

A Semantic Distinction “Either the predicate B

belongs to the subject A, as something which is contained (though covertly) in the conception A; or the predicate B lies completely out of the concept A, although it stands in connection with it. In the first instance, I term the judgment analytic, in the second, synthetic.”

Analytic judgments Kant: predicate

contained in subject General: true or false

solely in virtue of the meanings of its terms

Example: all bachelors are unmarried

Synthetic propositions10

Kant: predicate not contained in subject

General: truth value not determined by meanings of terms— depends on the world

Examples: all bachelors are unhappy

An Epistemological Distinction Avicenna (ibn Sina, 980-

1037): “Cognition can again be analyzed into two kinds. One is the kind that may be known through Intellect; it is known necessarily by reasoning through itself. . . . The other kind of cognition is one that is known by intuition [experience]. Whatever is known by Intellect . . . should be based on something which is known prior to the thing [that is, a priori].”

A Priori/A Posteriori Judgments A posteriori: dependent

on experience; can be known only by experience

A priori: independent of experience; can be known by reasoning alone

A Priori/A Posteriori15

A Posteriori: Hume, matters of fact: dependent on experience

A Priori: Hume, relations of ideas: can be known “by mere operation of thought”

A Metaphysical Distinction Gottfried Wilhelm Leibniz

(1646-1716): “There are also two kinds of truths, those of reasoning and those of fact. Truths of reasoning are necessary and their opposite is impossible: truths of fact are contingent and their opposite is possible.”

Necessary and contingent Necessary truths:

true in all possible worlds; can’t be false; opposite impossible

Contingent truths: true, but could be false; opposite possible

Necessary — A Priori

Enlightenment philosophers thought all and only a priori judgments were necessary

Necessary Contingent A Priori Yes No A Posteriori No Yes

Kripke’s Cases20

Necessary a posteriori Water is H2O Gold has atomic number 79

Contingent a priori Neptune causes

perturbations in the orbit of Uranus

Concepts and Judgments Avicenna distinguishes

knowledge of concepts from knowledge of judgments

Rationalists and empiricists can disagree about both

So, there are concept forms and judgment forms of each

Concept Rationalism Concept rationalism: There are innate concepts Leibniz: “. . . can it be denied that there is much that is

innate in our mind, since we are, so to speak, innate to ourselves, and since in ourselves there are being, unity, substance, duration, change, activity, perception, pleasure and a thousand other objects of our intellectual ideas? And as these objects are immediate objects of our understanding and are always present (although they cannot always be consciously perceived because of our distractions and wants), why should it be surprising that we say that these ideas, along with all that depends on them, are innate in us?”

Judgment Rationalism

Judgment rationalism: There are synthetic a priori truths

We can learn something about the world independently of experience— from reason alone

Leibniz frames the issue25

“There is the question whether the soul, in itself, is entirely empty, like a writing tablet on which nothing has yet been written (tabula rasa), (which is the opinion of Aristotle and the author of the Essay [Locke]), and whether everything that is inscribed upon it comes solely from the senses and experience; or whether the soul originally contains the principles of several notions and doctrines, which are merely roused on certain occasions by external objects, as I hold along with Plato and even with the Schoolmen. . . . Hence there arises another question, whether all truths are dependent on experience, that is, on induction and instances; or whether there are some which have yet another foundation.”

Kinds of Judgment

Analytic Synthetic

A Priori Yes ??

A Posteriori No Yes

Synthetic A Priori Truths? Avicenna

The whole is greater than its parts Things equal to the same thing are equal to each other

Descartes I think, therefore I am Anyone who thinks must exist while he/she thinks Nothing is made from nothing It’s impossible for anything to be and not be at the

same time What’s been done can’t be undone

Synthetic a priori truths? Leibniz

Principle of sufficient reason: there can be no fact without a sufficient reason why it should be so and not otherwise

Kant Every event has a cause Arithmetic (7 + 5 = 12) Geometry (between any two points lies one

line)

Synthetic a priori truths?30

Medieval philosophers Theology (God exists; The soul is immortal) Metaphysics (The world consists of

substances and their attributes; The will is free; Every substance has an essence)

Ethics (One ought to seek the good; Happiness is intrisically good; Courage is a virtue)

The Platonic Tradition Judgment of perception:

‘This is a triangle’ Mind is turned toward

object perceived But also to the form of a

triangle We perceive the thing as

a triangle because we apprehend the form

Objects and Abstract Forms “You are aware that students of geometry, arithmetic, and the kindred

sciences assume the odd and the even and the figures and three kinds of angles and the like in their several branches of science; these are their hypotheses, which they and everybody are supposed to know, and therefore they do not deign to give any account of them either to themselves or others; but they begin with them, and go on until they arrive at last, and in a consistent manner, at their conclusion? . . . And do you not know also that although they make use of the visible forms and reason about them, they are thinking not of these, but of the ideals which they resemble; not of the figures which they draw, but of the absolute square and the absolute diameter, and so on -- the forms which they draw or make, and which have shadows and reflections in water of their own, are converted by them into images, but they are really seeking to behold the things themselves, which can only be seen with the eye of the mind?”

Plato’s Philosophy of Mind

Form

Object

This is a triangle

Plato’s Philosophy of Mind35

Form

Object

This is a triangle

Participation

Perception

?

Forms explain how we can Think general thoughts Account for regularities Account for change Think the same thought

at different times Think the same thought

as each other Think veridical thoughts

Platonism’s problem

We don’t perceive the forms How do we know anything about them? Aristotle’s answer: abstraction Plato’s answers:

Recollection The Form of the Good

Plato’s Philosophy of Mind40

Form

Object

This is a triangle

Participation

Perception

Recollection

The Good

Augustine’s Philosophy of Mind

Form

Object

This is a triangle

Participation

Perception

Illumination

GodGod

The Rationalist’s Argument Leibniz: “For if some events can be foreseen before we

have made any trial of them, it is manifest that we contribute to them something of our own. The senses, although they are necessary for all our actual acquiring of knowledge, are by no means sufficient to give us the whole of our knowledge, since the senses never give anything but instances, that is to say particular or individual truths. Now all the instances which confirm a general truth, however numerous they may be, are not sufficient to establish the universal necessity of this same truth; for it does not at all follow that what has happened will happen in the same way.”

Leibniz’s Argument, cont’d “Whence it seems that necessary truths, such as we

find in pure mathematics and especially in arithmetic and geometry, must have principles whose proof does not depend upon instances nor, consequently, upon the witnesses of the senses, although without the senses it would never have come into our heads to think of them. . . . Logic also, along with metaphysics and ethics, of which the one forms natural theology and the other natural jurisprudence, are full of such truths; and consequently their demonstration can come only from the inner principles which are called innate.”

Universality45

Experience is always of particular instances

Knowledge immediately justified by experience is knowledge of particular instances

Universal truths don’t follow from their instances

So, experience can’t justify universal truths

Necessity Experience is always of contingent

matters of fact Knowledge immediately justified by

experience is knowledge of contingent matters of fact

Necessary truths don’t follow from contingent truths

So, experience can’t justify necessary truths

Universal, Necessary Truths

Metaphysics (e.g., Substances have properties)

Ethics (e.g., Happiness is good) Mathematics (e.g., The union of two sets

is a set) Natural science (e.g., F = ma; NaOH +

HCl —> NaCl + H2O)