Rationalism
•	Descartes
•	Spinoza
•	Leibnitz
•	Kant
Descartes (1596-1650)
•	Obsessed with questions of truth and doubt
–	How could one be certain in the absence of religious guidance and trustworthy senses
–	Typical rationalist program of finding clarity in thought
•	Find clear first principles that could act as a bedrock or foundation for thought
•	Could doubt everything except his own existence
–	Cogito ergo sum
–	Even the act of doubting presupposes a thinking entity
–	From such a clear first principle one could deduce all the rest – deductive reason was seen to be largely infallible.
Descartes’s dualism
•	Introduced dualism into modern philosophy and psychology
•	He was certainly not the first to see a sharp distinction between mind and body
•	Aristotle 
•	And all the Christian, Medieval thinkers.
Medieval dualism
•	Dualism between that which perishes and that which survives death
•	Based on Aristotle’s division into three parts
–	vegetative
–	sensitive
–	rational
•	The first two were vital forces that allow for movement and evidence of life
–	Only active to the extent that they were directed by the intellect or rational soul.
–	The body is a husk that gave evidence of life only when animated by a soul
Descartes’s distinction
•	Descartes made a sharper distinction between components 
•	Assigned the vital forces solely to the body with the rational soul entirely separate
•	Body is extended whereas the mind is not, “unextended substance”
•	And the body obeys mechanical laws because it is a part of the mechanical universe, whereas the mind does not
Cartesian Problems
•	Some claim this is a false distinction and has caused mischief
•	Issues
–	Camouflaged in the wooly Medieval conception
–	How do the mind and body interact?
–	How can something without mass and weight, something that is unobservable, influence something that has mass?
Descartes’s Solution – Interactionism
•	The mind and body interact at the pineal gland which takes care of all the translation work
•	Mind influences body through the agency of will
–	Not novel
–	But clearer in Descartes
•	Influence of the body on the mind is more complex.
–	The body is subject to passions created by sensation
–	These passions affect the mind
–	When all goes well, passions induce will to control the body, but they can also interfere with clear thought.
Descartes’s Theory of Mind Also Influential
•	Distrusted sensory data which are too unreliable to produce clear truths.
•	Assumed that we have innate ideas
–	Ideas are literally innate
–	We have the capacity to form certain ideas.
•	Intellectual faculties such as memory, intuition, and will. 
–	Had enormous influence
–	Led to much second and third rate philosophy 
–	Retarded French thought
Spinoza (1632-1677)
•	Middle class Jewish family in Amsterdam
–	Cherem (excommunication) for radical views
–	Seemed happy to leave religion behind
•	Cartesian and Stoic influences
•	Lay outside the mainstream of Continental thought 
–	“Rediscovered” toward the end of the last century
–	Partially because he was Jewish and thus had a different kind of background
–	And partially because he was geographically isolated
Spinoza’s Solution to Mind-Body
•	Parallelism
–	God and his creations are not separable
–	Therefore there can be no radical separation between mind and body
–	They are really two sides to the same coin – different language systems in contemporary thought
•	One important implication in terms of causality
–	The body is part of the physical world that obeys immutable laws
–	Mind (other side of the coin) must also be determined
–	Our mental lives are fully determined. 
Theory of Emotion & Passion
•	Largely influenced by the Stoics
•	Emotions vs. passions
–	Emotions were directed at clear objects
–	Passions merely generalized disruptions
–	Those we share with God are perfect and are emotions
–	Those that are not are imperfect and disruptive
–	Emotions are agents of the intellect
•	Help to channel thought
•	Commit us to reasoned action
–	Whereas the passions will disrupt
Truth and Emotion
•	Truth known most clearly when accompanied by emotion
•	We grasp truth as a kind of intuition
–	Our searching for ultimate truth will be guided by emotion
–	And we will experience pleasure when we get there
Spinoza’s Influence
•	Very little immediate
•	Rediscovered in 19th 
•	Now seen as forerunner of emotion/motivation
Leibniz (1646-1716)
•	Well educated
•	Also traveled widely
•	The usual non-academic jobs
•	For last 30 years studied science and most everything else
–	Important views of science, religion, and politics
–	Co-inventor of calculus
Contemporary of Locke
•	Much of his philosophy is an attempt to refute him
•	“Nothing is in the intellect which is not first in the senses”
•	To which he replied: Nothing except the intellect itself
Leibnitz’s Dualism and Monadology
•	Being consists of monads
–	Basically ideal points of psychic energy
–	However, when concentrated in one place they take on extension and give the impression of body
–	Mind and body obey different laws 
•	Adjusted by God to show perfect agreement
•	Pre-established harmony
•	Thus a parallelism account of dualism
His theory of consciousness
•	Each monad has mental activity
•	However, the mental activity of an individual monad is so small that it is not conscious
–	Distinction between mental activity and consciousness – first to do so
–	And first real idea of unconscious
•	Consciousness results when monads are combined
•	Consciousness exists on a continuum
•	A threshold as to what is conscious
•	Early psychological research issue
Mind forms thoughts
•	Conscious mental thought is not merely a result of sensation
•	It must be guided by higher mental structures through a process he called apperception
•	A kind of cognitive schema that guided thought.
•	A modern version of Platonic Forms or Aristotlean categories.
Leibnitz’s Influence
•	Great influence on the development of psychology in the 19th century.
–	.Psychophysics and thresholds of consciousness
–	Apperception and schematic thinking – Wundt
–	Conflict between ideas – Freud and others
•	Greater immediate influence than Kant, the greater thinker
Kant (1724-1804)
•	Academic life at Königsburg
•	Boring life
•	Great importance for all aspects of philosophy
–	Epistemology
–	Aesthetics
–	Moral
•	Psychological importance more indirect
The Major Rationalist Response to Hume
•	Bothered by Hume’s skepticism for religion and morality
–	If nothing could be known with certainty then theology and morality were on shaky grounds
–	So there must be a way of finding certainty
•	Importance of sense data
–	Did not deny the importance 
–	Did deny that they were sufficient
–	Empiricists would say we know because we perceive, but the rationalists would say that we perceive because we know. 
–	Top down vs. bottom up processing
Kant’s Analytic vs Synthetic Propositions
•	An old distinction
•	Analytic propositions are those that are true more or less by definition
–	Linguistic in nature
–	Predicate is logically implied by the subject
•	.Bodies have extension
•	.Bachelors are unmarried males
•	Synthetic -- the predicate bears only a contingent relationship to the subject
•	Not obviously but probalistically true
•	Empirical
•	Can be assessed only a posteriori
Can Synthetic Propositions Have A Priori Validity?
•	Critique of Pure Reason (1781)
•	Even the building blocks of Hume’s analysis of causality are not given in experience
•	Requires that we understand there are actually two objects which requires a notion of extended space
•	And that one follows the other, which requires time
•	One must have implicit categories of space and time
•	Categories must be innate because logically they must precede all experience.
Kantian Categories
•	There are 12 categories of thought --
•	Negation
•	Plurality
•	Causality
–	Necessary for any thought
Kant’s Moral Theory
•	Similar arguments for morality
•	Certain moral truths are self-evident
•	And logically necessary
•	The famous categorical imperative: “Act in such a way that the maxim of your action could serve as a universal law of nature”
Positive Influences on Psychology
•	A sensible rationalism that takes account of experience
•	Most sophisticated version of how mind shapes experiences
•	Notion of categories indirectly influential
•	Implied nativism 

Negative Influences on History of Psychology
•	Could be no science of psychology
–	Mental processes were fleeting and are of but not in the mind. 
–	Mental processes could not be measured, 
•	This served as a challenge for subsequent thinkers
•	Herbart and measurement
•	Fechner and psychophysics