Rationalism

Rationalism Plato Thinks only Forms are suitable objects of knowledge Forms tell us what is eternally and necessarily true Forms can be known purely intellectually

Rationalism Plato Is the great early hero of Rationalism Pure Reason is the route to knowledge

Rationalism Heroes of Rationalism Descartes Spinoza Leibniz

Knowledge A Priori Definition: Something is known a priori when it is a true belief whose justification does not depend on evidence from sense experience. Something is known a posteriori when its justification does depend upon sense experience

Knowledge A Priori Examples 5 + 7 = 12 I think, I am Nothing can be a both a circle and a square All bodies are extended

Knowledge A Priori Compare There are 12 eggs in this carton You exist This is a circle This is a body

Knowledge A Priori ‘Characteristics’ Everyone (who is mentally competent) will agree they are true No possible experience could lead us to doubt them Not just truths about our ideas of things, but of the things themselves Leibnitz: Truths of Reason Not justified by logic, since logic is itself known a priori

Knowledge A Priori Curiosities How can we know anything a priori? Known in the light of Reason. But what Reason? Just the ‘correct’ working of the Mind? By an intuition? How would an intuition count as knowledge? We can be fallibilists about a priori knowledge We know a priori that 5 + 7 = 12 But we can be wrong about 21341+7667543

Analytic Statements Definition: A statement is analytic when its truth may be known simply by knowing the meaning of the constituent terms A statement is synthetic otherwise

Analytic Statements Examples All bachelors are unmarried All bodies are extended If Cain killed Abel, then Abel is dead. If Al is heavier than Bob, and Bob is heavier than Chuck, then Al is heavier than Chuck 5 + 7 = 12

Analytic Statements Compare Cain killed Abel I am a bachelor

Analytic Statements Connection to A Priori The old view If something was known a priori then it was because it was expressed in an analytic statement If something was expressed in a synthetic statement it could only be a posteriori knowledge So all knowledge was either Analytic a priori or Synthetic a posteriori

Analytic Statements Connection to A Priori Hume’s problem Statements of cause were thought to be analytic But the idea of a necessary connection between the cause and effect couldn’t be got from the meanings of the terms So they can’t – by the old view – be a priori either But no number of observations of events will ever observe a necessity So we can’t have synthetic a posteriori knowledge of causes either

Analytic Statements Connection to A Priori Kant’s solution Note that even 5 + 7 = 12 isn’t really analytic The concept of ‘12’ is not contained in the concepts of ‘5’, ‘+’, ‘7’, or ‘=’ taken together or separately But it is known independently of all experience, so a priori Thus there is a category of synthetic a priori knowledge!

Analytic Statements Analytic Synthetic a priori a posteriori   Analytic Synthetic a priori All bachelors are unmarried All bodies are extended What will be will be Either Socrates is mortal or Socrates is not mortal 5 + 7 = 12 Nothing can be a both a circle and a square. If all men are mortal, and Socrates is a man, then Socrates is mortal a posteriori Cain killed Abel I am a bachelor Socrates is mortal There are 5 eggs here and also another 7 eggs here Analytic Statements

Analytic Statements Connection to A Priori Kant’s solution How is synthetic a priori knowledge possible? Our minds impose a certain structure upon our experience Space, time, causality are ways we organize our sensations

Innate Ideas Definition: An idea is innate if it does not derive from our experience of the world An idea is acquired otherwise An idea may be either a belief or a concept

Innate Ideas Innate beliefs Innate concepts 5 + 7 = 12 If all men are mortal, and Socrates is a man, then Socrates is mortal Nothing can be a both a circle and a square Innate concepts God Causation Space and Time

Innate Ideas Why imagine there are innate ideas? Some ideas are beyond the capacity of experience to justify, or even to produce 5 + 7 = 12 could not be discovered to be necessarily true by any number of experiences of the kind: ‘I got 5 eggs and then 7 more eggs, and now I have 12 eggs.’ We might try an induction, but why would we think induction is that reliable? It couldn’t give us necessity in any case.

Innate Ideas Note An idea being innate says nothing about its justification The relation between innate and a priori is not straightforward.

Rationalism Criteria for Rationalism More of a family of positions really. Tend to accept: 1. We have privileged modes of cognition 2. We have a priori knowledge 3. We have innate ideas

Rationalism 1. Privileged modes of cognition Yield a priori knowledge – independent of senses Deduction is one Logically deduced truths are indubitable We may have special intuitions Plato’s apperception of Forms Our own acquaintance with truths of logic, meaning, maths, etc.

Rationalism 2. We have a priori knowledge Plato thinks that’s because we have a special perception Others think it’s because of a special intuition Most think that nothing special is required more than a simple understanding of the nature of the concepts involved NB. It can’t be just by deduction because that’s how the knowledge of deduction is given to us

Rationalism 3. We have innate concepts Plato thinks that’s because we’ve been in contact with the Forms before our birth Kant thinks it’s because our minds are so constructed