Pioneers of Psychology
Summary
Chapter 2 Pioneering Philosophers of Mind: Descartes, Locke, and Leibniz
RENÉ DESCARTES AND THE MIND-BODY DISTINCTION
René Descartes (1596-1650) described the human mind and body as two interacting but
distinctly different entities, each requiring its own kind of analysis and explanation (mind-body
distinction).
René Descartes, John Locke, and Gottfried Wilhelm Leibniz are the foundations for a modern
discipline of scientific psychology.
Galileo Galilei (1564-1642) was an Italian scientist.
Descartes recognized that any point in space could similarly be defined by its numerical distances
from arbitrarily defined lines or planes, and further that the shape of a moving point’s course could
be defined by a sequence of such numbers.
Here was a potential method for integrating geometry (the study of shapes) with algebra (numerical
calculations)- the founding idea for a new disciple of analytic geometry, which has since become a
standard part of the mathematical curriculum.
DESCARTE’S METHOD AND ‘SIMPLE NATURES’
Descartes’s “first rule” for acquiring knowledge was: “never to accept anything as true unless … it
presented itself so clearly and distinctly in mind that there was no reason or occasion to doubt.”
Descartes started by arguing that the most elementary and fundamental properties of physical
phenomena, which he called simple natures, had to be those whose existence could not be analyzed
or doubted. The vast majority of our sensory impressions may seem vivid and obvious, he noted, but
they may be misleading.
After systematically doubting all of his sensory experiences, Descartes concluded that just two
physical properties qualified as simple natures:
1. Extension (the space occupied by a physical particle of body)
2. Motion (the movement of an extended particle or body throughout space)
These ideas seem to be similar to the primary and secondary qualities of physical matter of Galileo.
For Galileo, physical reality depended ultimately on the interactions of material particles having:
- The three primary qualities of shape, quantity, and motion. Everything in the universe arises
from these qualities.
- And when the primary qualities of the perceived object interact with the primary qualities
constituting the sensory organs, the result is the creation of secondary qualities, such as
sights, sounds, smells, and feelings.
Two treatises form Descartes:
1. Le Monde (The World) described his basic conception of the physical makeup of the universe,
before giving special attention to the subject of light and vision.
2. L’Homme (Man) he applied his physical principles to an analysis of living bodies.
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,DESCARTES’S PHYSICS
Descartes’s approach to physics resembled Democritus’s in that it accounted for the material world
on the basic of extended particles in motion, but differed from it by denying that they move about in
a void or vacuum.
Descartes hypothesized three kinds of particles corresponding to the classical elements of fire, air,
and earth:
1. He conceptualized the fire or heat particles as almost unimaginably tine s that when
aggregated they constituted “a virtually perfect fluid” capable of filling up space of any shape
or size.
2. Air particles, though larger than fire or heat particles, were still too small to be individually
perceived. More numerous than all other particles, they completely filled the spaces
between objects and, like the water in a fish pond, instantaneously moved into the spaced
vacated by moving objects.
3. All solid material objects, including the planets and comets as well as the earth and the
things on it, were presumably composed of accretions of earth particles, the third and
heaviest variety in Descartes’s hypothetical universe.
MECHANISTIC PHYSIOLOGY
A few others before Descartes had begun to explain living bodies mechanistically. Galileo, for
example, had analyzed the body’s bones and joints as if they were a system of physical levers.
Descartes noted that the brain contained cavities, or ventricles, filled with a clear yellowish liquid he
called animal spirits (today known as cerebrospinal fluid).
Descartes’s idea of a reflex:
1. Vibrations from a hot fire (A)
2. Stimulate sense receptors in the foot (B)
3. Thus, pulling a fiber in the long nerve (cc)
4. Which thugs open a valve in the brain (de)
5. Animal spirits contained in the brain cavity (F)
6. Then enter the long nerve and travel back down
through it, resulting in the withdrawal of the foot from
the fire.
Although he did not use the exact term, this diagram above
illustrates a fundamental neurophysiological principle now
known as a reflex – a sequence in which a specific stimulus
from the external world (heat form the fire) automatically
elicits a specific response (pulling away).
A reflex in which the response occurs involuntarily, and in the
same organ that senses its stimulus, is referred to by
psychologists today as an unconditioned reflex.
Descartes’s model also accounted for another, more complicated type of reflex, in which the stimulus
elicits a different kind of acquired response as a product of experience and learning.
Descartes recognized that behavioral responses may also be influenced by internal emotional factors,
and these he explained as the result of localized “commotions” – currents or eddies – that arise in
the pool of animal spirits in the brain.
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,RATIONAL QUALITIES OF THE MIND
In the Discourse on Method, Descartes described how, when he first began to systematically doubt,
everything seemed to be uncertain, including the most obvious and vivid of sensory impressions.
But he could not doubt that he was doubting. He summarized his conclusion with the simple
statement “I think, therefore I am,” (Cogito ergo sum).
This train of thought led him to identify other ideas that, while “real,” also seemed incapable of being
represented by a single experience: “perfection,” “unity,” “infinity,” and the geometrical axioms
came to mind.
Descartes concluded that these ideas, independent as they are of specific sensory experience (but
capable of being suggested or alluded to by experience), must derive from the nature of the thinking
soul itself. Accordingly, he called them the innate ideas of the mind.
INTERACTIVE DUALISM
Because of his sharp distinction between the body and the mind, Descartes is referred to
as a dualist. He adds something new by emphasizing the extent to which important
phenomena are the result of neither body nor mind acting alone, but rather of the many
possible kinds of interactions between the two (interactive dualism).
Throughout the 1640s, Descartes developed his dualistic ideas in an extensive
correspondence with a remarkable royal person, Princess Elizabeth of Bohemia.
From today’s perspective, some of Descartes’s strangest theorizing discussed how the
mind gets information form the body’s senses. He was troubled by the fact that the mind
somehow manages to consciously experience a single, upright and full-sized
object although upside-down images of external object onto the retinas at
the backs of the two eyeballs.
He learned about the pineal gland, a small, pinecone-shaped structure near
the center of the brain and extending partially into a large ventricle. He
speculated that here is where sensations form the divided body are
reunified for presentation to the soul.
The pineal gland’s strategic location within the spirit-filled ventricle also
meant that it was ideally placed to sense the commotions, or eddies, or the
animal spirits that he presumed were the cause of emotions. He called the
mind’s conscious experience of these commotions the passions- the
conscious awareness of feelings such as love.
JOHN LOCKE AND THE EMPIRICIST TRADITION
In 1690 the English philosopher and physician John Locke (1632-1704) published his important
book, An Essay Concerning Human Understanding, which attracted the attention of Gottfried
Leibniz in Germany.
Leibniz wrote the manuscript New Essays on Human Understanding (Nouveaux Essais sur
l’Entendement Humain), a fictional representative of Locke engages in Platonic-style dialogue with a
mouthpiece for Leibniz himself. Locke died just as the work was finished, and Leibniz, not wanting to
dispute with a dead author, put his manuscript aside and it remained unpublished until a half-
century after his own dead.
Locke adopted many of Descartes’s basic ideas regarding physics and physiology and used them as
the foundation for an empiricist theory of knowledge.
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, REVOLUTION AND TOLERANCE
Locke became a follower and friend of the eminent chemist Robert Boyle (1627-1691). Boyle
had previously conducted famous experiments demonstrating what became known as Boyle’s
law: the fact that the volume of a gas varies inversely with the pressure exerted upon it.
POLITICAL INVOLVEMENT
Sir Anthony Ashley Cooper (1621-1683) had been a prominent member first of Olivers
Cromwell’s Commonwealth government, and then, after that failed, of the new restoration
parliament where he became a favorite of King Charles ll.
Ashley found Locke to be an intelligent and broadly educated gentlemen as well as a skillful
physician, and Locke found in Ashley a mature political mentor whose diverse interests and
tolerant political attitudes meshed perfectly with his own.
AN ESSAY CONCERNING HUMAN UNDERSTANDING
At his starting point Locke invoked Aristoteles’s conception of the inexperienced mind as a
tabular rasa – a blank slate – or, in Locke’s term, a “white paper void of alle characters.”
In answer to the question: “How comes this blank slate to be furnished?” he replied: “in one word,
from experience; in [which] all our knowledge is founded.”
Locke saw the mind essentially as a receptacle for information from the outside world, and often a
passive one.
In terms of the kinds of experiences the mind has, Locke proposed there were just two:
1. Sensations of objects in the external world
2. Reflections of the mind’s own operations
These experiences produce representations or ideas in the mind that become recallable in the form
of memories after leaving immediate consciousness.
An inexperienced infant’s earliest sensations and reflections presumable produce the most basic
simple ideas: notion such as redness, loudness, or coldness; and of states such as wanting, seeing,
liking, and disliking from inner reflections.
With repeated experience, simple ideas get combined by the mind in varying ways to produce
complex ideas. For example, redness, roundness, and sweetness may combine to produce the
complex idea of an apple; the notions of an apple and desiring may combine to produce part of the
still more complex idea of hunger.
Locke’s friend William Molyneux (1656-1696) provided a famous illustration of this point in the
hypothetical case of a man blind from birth who had learned to distinguish a ball from a cube by the
sense of touch.
KINDS OF KNOWLEDGE
After describing the basic nature of ideas, Locke turned his attention to the nature of knowledge,
which he defined as “the perception of the connection and agreement, or disagreement and
repugnancy, of any of our ideas.”
A very few such perceptions are immediate and irresistible, such as recognizing the difference
between something black and something white, or between a circle and a triangle. Locke referred to
this as intuitive knowledge.
Demonstrative knowledge is exemplified by geometric or logical reasoning in which a stepwise series
of deductions involving axioms results in a conclusion that is not obvious but definitely true.
For Locke the largest proportion of human knowledge was neither intuitive nor demonstrative, but
rather sensitive knowledge, created by the particular patterns of sensory experiences people have.
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