Rationalism - Daniel Bonevacphilosophical.space/philosophy/Leibniz.pdf•Concept rationalism: There...

Rationalism

Saturday, October 12, 19

• 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)

Rationalism and Empiricism


• 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

Concepts and Judgments


• 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?”

Concept Rationalism


• “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?”

Concept Rationalism


• “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.”

1. A Semantic Distinction


• Kant: predicate contained in subject

• General: true or false solely in virtue of the meanings of its terms

• Example: all bachelors are unmarried

Analytic judgments


• Kant: predicate not contained in subject

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

• Examples: all bachelors are unhappy

Synthetic propositions


• 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].”

2. An Epistemological Distinction


•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 Posteriori Judgments


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

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

A Priori/A Posteriori


• Judgment rationalism: There are synthetic a priori truths

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

Judgment Rationalism


• “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;”

Leibniz frames the issue


• “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.”



Rationalism? Empiricism?

Analytic Synthetic

A priori

A posteriori


Judgment Empiricism

Analytic Synthetic

A priori

A posteriori


Judgment Rationalism

Analytic Synthetic

A priori

A posteriori


• 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.”

3. A Metaphysical Distinction


• Necessary truths: true in all possible worlds; can’t be false; opposite impossible

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

Necessary and contingent


Necessary and A Priori

Necessary Contingent

A priori

A posteriori


• Necessary a posteriori?

• Water is H2O

• Gold has atomic number 79

• Contingent a priori?

• The length of this stick is one meter.

Kripke’s Cases


Necessary and A Priori

Necessary Contingent

A priori

A posteriori


Judgment Rationalism, 1

Analytic Synthetic

A priori

A posteriori


Judgment Rationalism, 2?

Analytic Synthetic

Necessary

Contingent ???


• Avicenna

• The whole is greater than its parts

• Things equal to the same thing are equal to each other

• Descartes

• I think, I am

Synthetic A Priori Truths?

• 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


• 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?


• 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)

Synthetic a priori truths?


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.”


Universality

• 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


Particular to General • Fa & Ga

• Fb & Gb

• Fc & Gc

• .

• .

• .

• _________

•All F are G

This argumentisn’t valid!

Some other premisemust be added bysomething otherthan experience


Leibniz’s Argument, cont’d

•“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.”


The Rationalist’s Argument

• “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.”


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 (nontrivially) from contingent truths

• So, experience can’t justify necessary truths


Contingent to Universal

• Fa & Ga

• Fb & Gb

• Fc & Gc

• .

• .

• .

• _________

•Necessarily, All F are G

This argumentisn’t valid!

Some other premisemust be added bysomething otherthan experience


Contingent to Cause • Fa then Ga

• Fb then Gb

• Fc then Gc

• .

• .

• .

• _________

• Therefore, Fs cause Gs

Ambiguous: Does the necessityattach to the conclusionor to the connection?

Necessarily, if Fa then Ga, Fb then Gb,...,then Fs cause Gs

But that doesn’t follow


Contingent to Universal

• Fa & Ga

• Fb & Gb

• Fc & Gc

• .

• .

• .

• _________

•Necessarily, Fz & Gz

Ambiguous: Does the necessityattach to the conclusionor to the connection?

Necessarily, if Fa & Ga, Fb & Gb,...,then Fz & Gz

But that still doesn’t follow



•“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.”


Universal, Necessary Truths

• Examples of alleged synthetic a priori truths:

• Metaphysics (e.g., Substances have properties, Substances stand in relations, Events take place in time, ....)




• Ethics (e.g., Happiness is good, Courage is a virtue, The good is to be sought, Evil is to be avoided, Treat others with respect, Act on principle, ....)




• Mathematics (e.g., Every number has a successor; There is an infinite set; The union of two sets is a set; The power set of a set is a set)




• Natural science (e.g., F = ma; PV = nRT; P = NV; N = M + K/c2; NaOH + HCl —> NaCl + H2O—these are a posteriori, but lawlike; something a priori must underlie them—such as Every event has a cause, Conservation of energy, etc.)


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