1. The origin of concepts and the nature of knowledge: where do
ideas/concepts and knowledge come from?
i.
Introduction
Key words/phrases table
For this section of the course, you will need to know:
1. Concept empiricism: all concepts are derived from experience
1.1 The tabula rasa
1.2 Impressions and ideas
1.3 Simple and complex concepts
1.4 Strengths of this view
2. Issues with concept empiricism:
2.1 Does the concept of ‘simple ideas’ make sense? Do all simple ideas come from sense
experience? Do all complex ideas/concepts relate to sense experience? Do some concepts
have to exist in the mind before sense impressions can be properly experienced?
2.2 Concept innatism (rationalism): there are at least some innate concepts:
2.2.1 Descartes’ Trademark argument
2.2.2 Innate concept of physical substance
2.2.3 Innate concepts of numbers
2.2.4 Innate concepts of universals (i.e. Beauty and Justice).
2.2.5 Innate structures
2.3 Concept empiricist arguments against concept innatism:
2.3.1 Alternative explanations (no such concept or concept re-defined as based on
experiences).
2.3.2 Locke’s arguments against innatism, and Leibniz’s responses.
3. Knowledge empiricism: all synthetic knowledge is a posteriori and all a priori knowledge is
merely analytic.
3.1 Hume’s Fork
4. Issues with knowledge empiricism:
4.1 Arguments against knowledge empiricism: the limits of empirical knowledge (Descartes’
sceptical arguments.
4.2 Knowledge innatism (rationalism): there is at least some innate a priori knowledge (Plato
and Leibniz)
4.2.1 Knowledge empiricist arguments against knowledge innatism: alternative
explanations (no such knowledge, in fact based on experiences or merely
analytic); Locke’s arguments against innatism; its reliance on the non-natural.
4.3 Intuition and deduction thesis (rationalism): we can gain synthetic a priori knowledge
through intuition and deduction (Descartes on the existence of the self, God and the
external world).
4.3.1 Knowledge empiricist arguments against the intuition and deduction thesis.
Key words and phrases
Ideas
Ideas = concepts. Having a concept of something
= being able to recognise it, think about it and
distinguish it from other things.
Simple Ideas
Ideas that cannot be broken down into parts –
e.g. ‘white’ and ‘cold’.
Complex ideas
Ideas that can be broken down into parts – e.g.
‘golden mountain’ and ‘unicorn’.
Impressions
Experiences/sensations, like the experience of
seeing snow, or the sensation of pain.
Outward impressions
Experiences of the world outside us – e.g. from
sight, hearing, touch, taste and smell.
Inward impressions
Experiences of things going on inside us – e.g. the
experiences of pain, pleasure, happiness, sadness
and anger.
Propositions
Sentences that make a claim about the way the
world is – e.g. ‘There is a cat on the mat’ or ‘I am
thinking about a dragon’.
Analytic proposition
Propositions that are true by definition – i.e. true
just in virtue of the meaning of the words within
them. E.g. ‘All bachelors are unmarried men’.
Synthetic propositions
Propositions that are not true by definition, but
true or false depending on the way the world is.
E.g. ‘all men are mortal.’
Necessary truths
A truth that cannot be denied without
contradiction. Examples: 2+2=4; triangles have
three sides; all bachelors are unmarried men.
Contingent truths
A truth that can be denied without
contraditiction. Examples: the sky is blue; grass is
green; Winston Churchill was Prime Minister.
Arguments
An argument is a series of propositions intended
to support a conclusion. The propositions offered
in support of the concusion are called reasons or
premises.
Deductive arguments
Arguments where the truth of the conclusion is
guaranteed by the truths of the premises. For
example: All men are mortal; Socrates is a man;
so Socrates is mortal.
Inductive arguments
Arguments where the truth of the conclusion is
not fully guaranteed by the truth of the premises.
For example: The sun has always risen in the past,
so the sun will continue to rise in the future.
A priori knowledge
Propositional knowledge that is acquired
independently of experience (prior to it).
Examples: the knowledge that 2+2=4 or that all
bachelors are unmarried.
A posteriori knowledge
Propositional knowledge that is acquired from
experience (after it). Examples: the knowledge
that snow is white, or that the Atlantic is smaller
than the Pacific.
Innate knowledge
Propositional knowledge that exists in the mind at
birth, and so is not acquired by experience.
Empiricism
The philosophical position that all of our ideas,
concepts, beliefs and knowledge are acquired
from experience.
Concept empiricism
All concepts are derived from experience. There
are no innate conepts.
Knowledge empiricism
The theory that there can be no a priori
knowledge of synthetic propositions about the
world (outside of my mind), i.e. all a priori
knowledge is of analytic propositions, while all
knowledge of synthetic propositions must be
checked against sense experience.
Rationalism
The philosophical position that reason, rather
than experience, is the most important source of
ideas and knowledge.
1. Concept empiricism: all concepts are derived from experience
1.1
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The tabula rasa:
According to the empiricist John Locke, the mind is a ‘tabula rasa’ – a blank slate.
Therefore all ideas/concepts are derived from experience – from impressions.
There are two types of impressions:
- Impressions of sensation: our experience of objects outside the mind, perceived through
the senses. This gives us ideas of ‘sensible qualities’.
- Impressions of reflection: our experience of ‘internal operations of our minds’, gained
through introspection or an awareness of what the mind is doing.
Locke uses the term ‘idea’ to cover sensations and concepts!
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‘Let us then suppose the mind to have no ideas in it, to be like white paper with nothing written on it. How then does it
come to be written on? From where does it get that vast store which the busy and boundless imagination of man has
painted on it – all the materials of reason and knowledge? To this I answer, in one word, from experience. Our
understandings derive all the materials of thinking from observations that we make of external objects that can be
perceived through the senses, and of the internal operations of our minds, which we perceive by looking in at
ourselves.’ (Locke, An Essay Concerning Human Understanding, II, 1, par.2)
1.2
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Impressions and ideas
Hume develops John Locke’s empiricist philosophy.
Hume argues that what we are immediately and directly aware of are ‘perceptions’.
‘Perceptions’ are divided into ‘impressions’ and ‘ideas’, the difference between the two
being marked by a difference of ‘forcefulness’ and ‘vivacity’, so that impressions relate
roughly to ‘feeling’ (or ‘sensing’) and ideas to ‘thinking’.
Hume argues that ideas are faint copies of original sense impressions (Hume’s Copy
Principle). For example, my ideas of whiteness and coldness are copies of my sensation of
the whiteness and coldness of snow. Because this sensation was forceful and vivid, it
stamped a copy of itself on my mind. This copy is considerably fainter than the original
sensation. If I create other ideas from it, they will be fainter still.
All of our ideas are built up from copies of our impressions, by combining, separating,
augmenting and diminishing them.
Hume, following Locke, divides impressions into those of ‘sensation’ and those of
‘reflection’. Impressions of sensation derive from our senses, impressions of reflection
derive from our experiences of our mind, including emotions for Hume.
Impressions = the more lively sensations that we have when we see or hear or feel or love or hate.
Ideas = the less lively sensations that we have when we think about seeing, hearing, feeling etc.
1.3 Simple and complex concepts
‘But although our thought seems to be so free, when we look more carefully, we’ll find that it is really confined within
very narrow limits, and that all this creative power of the mind amounts merely to the ability to combine, transpose,
enlarge or shrink the materials that the senses and experiences provide us with.’
Hume, Enquiry Concerning Human Understanding, Enquiry 1, section 2.
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Both Locke and Hume distinguish between simple and complex ideas.
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They argue that ideas which do not come directly from experience (e.g. the idea of a
unicorn) are all built out of simpler ideas that do come from experience (the ideas of a horse
and a horn).
For example, I see a mountain and something golden, and combine the ideas generated by
these impressions to form the idea of a golden mountain (Hume’s example).
1.4 Strengths of this view
 It fits with our experience of the acquisition of ideas – we acquire ideas of things as we
experience them, and not before (Locke).
 It explains why people who lack certain kinds of sensation also lack the corresponding ideas
– e.g. why blind people have no ideas of colours, and deaf people no idea of sounds (Hume).
 It gives us a way of resolving philosophical problems – clarify the ideas on which they are
based and the problems will disappear. Hume applies this to philosophical problems about
causation, God, morality and the self.
Hume’s two arguments for concept empiricism:
1) When we analyse our thoughts or ideas—however complex or elevated they are—we always find them to be
made up of simple ideas that were copied from earlier feelings or sensations. Even ideas that at first glance seem
to be the furthest removed from that origin are found on closer examination to be derived from it. The idea of
God—meaning an infinitely intelligent, wise, and good Being—comes from extending beyond all limits the
qualities of goodness and wisdom that we find in our own minds. However far we push this enquiry, we shall find
that every idea that we examine is copied from a similar impression.
2) If a man can’t have some kind of sensation because there is something wrong with his eyes, ears etc., he will
never be found to have corresponding ideas. A blind man can’t form a notion of colours, or a deaf man a notion
of sounds.
Hume, An Enquiry Concerning Human understanding, Section 2, p.8
2. Issues with concept empiricism:
2.1 Does the concept of ‘simple ideas’ make sense? Do all simple ideas come from sense
experience? Do all complex ideas/concepts relate to sense experience? Do some concepts
have to exist in the mind before sense impressions can be properly experienced?
(a) Does the concept of ‘simple ideas’ make sense?
 Simple concepts can be analysed further.
 For example the simple concept of a mountain can be further analysed into the concept of
rock, the concept of snow, the concept of grass, etc.
 Although these collections of ideas do not necessarily add up to the complete concept of
‘mountain’.
 The question is, when does the analysis stop? When do we find a simple impression?
 This demonstrates a difficulty for the empiricist in working out the details of their theory of
impressions and ideas.
(b) Do all simple ideas come from sense experience?
 Hume’s missing shade of blue: if it is possible to form an idea without a corresponding
impression (the idea of the missing shade of blue without the impression of this shade of
blue) this goes against the principle that nothing can exist in the mind that has not come
through the senses , undermining the most basic tenet of empiricism.
‘Can he fill the blank [shade] from his own imagination, calling up in his mind the idea of that particular
shade, even though it has never been conveyed to him by the senses? Most people, I think, will agree that
he can. This seems to show that simple ideas are not always, in every instance, derived from corresponding
impressions. Still, the example is so singular that it’s hardly worth noticing, and on its own it isn’t a good
enough reason for us to alter our general maxim.’
Hume, An Enquiry Concerning Human Understanding, Enquiry 1, Section 2,
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Hume does not seem to adequately respond to the problem he poses, arguing that this is
simply an exception to the general rule. However, if we can form this concept without having
had an impression, why should we not be able to form others?
One response is to say that missing shade of blue is a complex concept and can be formed
from the idea of ‘blue in general’ and the concepts of ‘dark’ and ‘light’.
However, then all ideas of colour would be complex concepts – how would we form the simple
concept?
The empiricist could also respond that we cannot actually form the concept of the missing
shade of blue, but the implications of this would be that we would have to experience millions
of different shades of colours to form the concepts of each colour.
(c) Do all complex ideas/concepts relate to sense experience?
 We can have concepts of things we have never experienced; for example I can form the
concept of Italy having never been there and I can form the concept of an atom without being
able to see it.
 How do we acquire concepts of abstract concepts such as freedom or justice? We don’t seem
to have sense impressions of these concepts.
 Empiricists might respond that with abstract concepts there will be a complex route back to
experience, i.e. we can form the concept of justice from observing justice acts.
 Do relational concepts (e.g. ‘being near’, ‘being far’, ‘on’, below’, ‘behind’ etc.) derive from
impressions? I can have a sense impression of a cat and a mat but I don’t seem to have a sense
impression of ‘on-ness’ so, according to the empiricist, how would one form the concept of
the cat on the mat?
(d) Do some concepts have to exist in the mind before sense impressions can be properly
experienced?
 Our brains must have some concepts or structures already in place for our sense experiences
to make sense.
 For example, Condillac’s statue would experience a flow of sense data without being able to
categorise this sense data. The statue would experience what William James has called ‘a
blooming, buzzing confusion.’
 Immanuel Kant argued that there must be conceptual schemes in place for us to categorise
and understand our sense experiences.
2.2 Concept innatism (rationalism): there are at least some innate concepts.
Locke (who denied the existence of innate ideas) defines innate ideas as:
‘[S]ome primary notions... Characters as it were stamped upon the Mind of Man, which the Soul
receives in its very first Being; and brings into the world with it.’
Locke, An Essay Concerning Human Understanding, 1, 2, par. 1
2.2.1
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Descartes’ Trademark argument
Descartes tried to prove the existence of God in his Trademark argument by arguing that
we have an innate idea of God that has been ‘stamped’ on our mind by God.
Descartes argues that humans have an idea of a perfect and infinite being (God).
However, as humans are finite and imperfect, we cannot have created this idea
ourselves. The idea must come from an infinite and perfect being – God – therefore
proving God’s existence.
‘But these attributes [of God’s] are so great and eminent that the more attentively I consider them, the less I am
persuaded that the idea I have of them can originate in me alone. And consequently I must necessarily conclude
from all I have said hitherto, that God exists; for, although the idea of substance is in me, for the very reason that I
am a substance, I would not, nevertheless, have the idea of an infinite substance, since I am a finite being, unless
the idea has been put into me by some substance which was truly infinite.’
Descartes, Meditations, page 124.
Hayward, Jones and Cardinal give Descartes’ Trademark argument in a formal style:
- Premise 1: The cause of anything must be at least as perfect as its effect [The Causal Principle]
- Premise 2: My ideas must be caused by something.
- Premise 3: I am an imperfect being.
- Premise 4: I have the idea of God, which is that of a perfect being.
- Intermediate conclusion 1: I cannot be the cause of my idea of God. (From premises 1,2,3 and 4).
- Intermediate conclusion 2: Only a perfect being (that is, God) can be the cause of my idea of God. (From
premise 1 and 4 and IC1).
- Main conclusion: God must exist. (From premise 4 and IC2).
Hayward, Jones and Cardinal, AQA AS Philosophy, p.126).
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Problems with Descartes’ Trademark argument:
- There are problems with Descartes’ Causal Principle (that ‘there must be at least as much
reality in the efficient and total cause as in its effect’ Meditations) because there seem to be
examples of effects have more perfection or reality than their causes. Examples: a match
causing a bonfire; a whisper causing an avalanche; the natural process of evolution. So the
idea of God needn’t come from God.
- Humans don’t have the idea of infinity (the most humans can have is the idea of the
opposite of finite). So, if humans don’t have an idea of an infinite being then Descartes’
argument fails.
- The idea of God is incoherent (e.g. the paradox of the stone). So the idea of God is unclear
and would not be caused by God but could have been caused by Descartes himself.
- The idea of an all-powerful God is not universal and therefore this idea may have arisen at
one point in history rather than being innate.
- Empiricists can explain how we have the idea of God through abstracting qualities and
characteristics we observe in the world. For example, we experience wise, kind and strong
people and abstract out these characteristics infinitely to form the idea of an omniscient,
omnibenevolent and omnipotent being, God.
2.2.2 Innate concept of physical substance
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Descartes argues that the concept of a physical object does not derive from sense
experience, but is innate.
He argues this through using the example of a block of wax. When cold, the wax sounds,
feels, looks and smells a certain way, for example it is hard and makes a sound when struck
with a finger. However, when the block of wax is melted, it changes shape and colour, it
feels and smells differently and it no longer makes a sound when struck by a finger.
Therefore, all the original sensory qualities of the wax have changed.
However, Descartes argues that we would still believe that this is the same block of wax.
As our senses cannot tell us that this is the same block of was – because all the sensory
qualities of the wax have changed – it is our understanding that tells us that this is the same
wax.
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Therefore, our idea of physical objects belongs in the understanding and thus is innate.
2.2.3. Innate concepts of numbers
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Both Plato and Descartes argued that our concepts of numbers are innate.
Plato argues that we cannot have sensory experiences of numbers – for example, we can
have sensory experiences of pairs of things but never the number 2 itself – so our concepts
of numbers must be innate.
Plato argues that we encounter numbers in the World of Forms – a realm of pure thought –
before birth.
Empiricists can reply that we form the concepts of numbers from abstracting out from
sensory experiences of collections of objects in the world.
However, Descartes argues that we can form the concept of a shape with one thousand
sides without being able to form a clear image of this shape. So, we can form concepts (we
can understand) numbers and shapes that we have never encountered.
So, the concepts of numbers and shapes are not acquired through sensory experience but
exist in the innately in the mind.
2.2.4. Innate concepts of universals (i.e. Beauty and Justice).
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Plato argues that our concepts of universals such as beauty and justice are innate and we
encounter these universals in the world of forms before birth.
He argues that we cannot acquire these concepts through sensory experience because we
only ever observe particular examples of beautiful or just things, never Beauty or Justice
itself.
Additionally, in order to be able to recognise when particular things are beautiful or
particular actions are just, we must first possess the concepts of beauty and justice. If we did
not possess these concepts, we wouldn’t be able to recognise or learn about beautiful or
just things.
2.2.5. Innate structures.
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Kant believed that humans possess innate concepts in their minds in order to structure,
categorise and make sense of their sensory experiences.
‘Thoughts without content are empty; intuitions [impressions] without concepts are blind.’ (Kant,
Critique of Pure Reason).
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Therefore, rather than the human mind passively receiving sensory information, the human
mind is active in shaping sensory experiences of the world.
 Examples of innate concepts for Kant include: causation; time and space, and unity.
 Noam Chomsky has also argued that humans innately posses the capacity to learn language
– just hearing and experiencing language would not be enough for humans to learn
language.
2.3 Concept empiricist arguments against concept innatism:
2.3.1 Alternative explanations (no such concept or concept re-defined as based on
experiences).
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2.3.2
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Empiricist arguments against an innate idea of God:
- Our concept of God comes from us abstracting qualities we observe in the world. For
example, we experience wise, kind and strong people and abstract out these
characteristics infinitely to form the idea of an omniscient, omnibenevolent and
omnipotent being, God.
- Some Empiricists might also argue that not all humans have the concept of God. They
might also argue that we do not have the concept of an infinite being – we only have a
negative concept of infinite as the opposite of finite.
Empiricist arguments against an innate idea of physical substance:
- we can form the concept of extension through abstracting from our changeable
sensory experiences.
Empiricist arguments against innate ideas of numbers:
- We acquire the concepts of numbers from abstracting out from our experiences of
collections of objects. For example, by having experiences of pairs of things, we can
recognise what they have in common and abstract out the concept ‘two’.
Empiricist arguments against innate ideas of universals such as beauty and justice:
- We have many experiences of beautiful objects (e.g. paintings, sunsets) and we
recognise what each of these experiences has in common and abstract out the concept
of ‘beauty’ from these experiences. Similarly with justice; we abstract out the concept of
justice from recognising similarities in our experiences of just acts.
Locke’s arguments against innatism and Leibniz’s responses.
In Locke’s Essay Concerning Human Understanding, he sets out to show that innate
ideas do not exist (that the mind is indeed a Tabula Rasa).
Locke’s arguments against the existence of innate ideas are:
(a) Innate ideas are not necessary:
‘... men can get all the knowledge they have, and can arrive at certainty about some things, purely by
using their natural faculties, without help from any innate notions or principles.’
Locke, An Essay Concerning Human Understanding,1,2, par.1
- Locke argues that innate ideas are unnecessary because the acquisition of all concepts can
be explained with reference to sensory experience. For example, Locke argues that it is clear
that we experience colours through our sight and therefore, why would God or nature also
give us an innate idea of colour if we can also acquire this concept through experience?
- Therefore, if all ideas can be explained with reference to experience, why should we
suppose that we have innate ideas? Using Occam’s razor, we should go for the simpler
explanation – that all ideas are acquired from experience.
‘Everyone will agree, presumably, that it would be absurd to suppose that the ideas of colours are innate in a creature
to whom God has given eyesight, which is a power to get those ideas through the eyes from external objects. It would
be equally unreasonable to explain our knowledge of various truths in terms of innate ‘imprinting’ if it could just as
easily be explained(b)
through
abilities
to come
to know
things.’
Thereour
areordinary
no universal
ideas,
so there
are no
innate ideas:
Locke, An Essay Concerning Human Understanding,1,2, par.1
‘Nothing is more commonly taken for granted than that certain principles ... are accepted by all
mankind. Some people have argued that because these principles are (they think) universally
accepted, they must have been stamped onto the souls of men from the outset.’
Locke, An Essay Concerning Human Understanding,1,2, par.2
- Locke argues that there are no innate ideas because there are no ideas which are universally held
(held by everyone).
- To demonstrate this, Locke uses two examples from logic: the law of identity, ‘Whatever is, is’ and
the law of non-contradiction, ‘it is impossible for the same thing to be and not to be’. He argues that
while these are accepted as strong contenders for innate ideas, they are not universally held because
‘children and idiots’ do not possess these concepts.
‘Children and idiots have no thought – not an inkling – of these principles, and that fact alone is enough to destroy
the universal assent that any truth that was genuinely innate would have.’
Locke, An Essay Concerning Human Understanding,1,2, par.5
- Leibniz responds to this criticism by saying that ‘children and idiots’ do possess these concepts;
however they are unable to fully articulate these concepts in words. He argues that they show they
possess these concepts due to the ways in which they act. Therefore, these concepts could be universal.
- Leibniz also responds by arguing that innate ideas do not need to be universal:
(i) He argues firstly that not all universal ideas are innate; even if the whole world smoked, this would
not mean that the desire to smoke was innate.
(ii)Secondly, not all innate ideas need to be universal as God could choose to give certain ideas to only
some people.
(c) The transparency of our minds:
- Some Innatists argue that innate ideas exist in the mind but people are not always aware of them
until later in life.
-However, Locke argues that if the mind has certain ideas imprinted on it then the person would be
aware of these ideas – the mind is transparent.
- If we do not know we have an idea of something/we have never thought about it, then how can the
idea be ‘in’ our minds?
‘To imprint anything on the mind without the mind’s perceiving it seems to me hardly intelligible. So
if children and idiots have souls, minds, with those principles imprinted on them they can’t help
perceiving them and assenting to them.’
Locke, An Essay Concerning Human Understanding,1,2, par.5
- Leibniz’s responds by arguing that we can acquire a concept without being conscious of doing so, for
example ‘absorbing’ the tune of a song playing in the background without being aware of doing so.
Therefore, if we can possess ideas subconsciously, then this undermines Locke’s argument that the
mind is transparent.
(d) It would not be possible to distinguish innate ideas from ideas acquired through experience.
- If some Innatists claim that innate ideas exist but people may not become conscious of them until
later in life then how can we distinguish between innate ideas and ideas gained through experience?
- Leibniz replies by saying that we can distinguish between innate ideas and ideas acquired through
experience because innate ideas are necessary, such as the truths of mathematics, geometry and logic.
Because these types of truths are eternal, they cannot have been acquired from experience but only
through reason.
(e) Innatism relies on the supernatural.
- Many Innatists claim that our innate ideas are imprinted on our minds before birth by God.
- Locke argues that because empiricism can explain how we acquire ideas naturally, with no need for
God/ the supernatural, it is a more plausible theory of the origin of our ideas.
- However, some Innatists claim that we have innate ideas due to the way our brains have evolved, so
innatism does not have to rely on the supernatural.
3. Knowledge empiricism
 All synthetic knowledge is a posteriori and all a priori knowledge is merely analytic.
3.1 Hume’s Fork
‘All the objects of human reason or enquiry fall naturally into two kinds, namely relations of ideas
and matters of fact.’ (Hume, An Enquiry Concerning Human Understanding, Enquiry 1, section 4.)
- Hume divides all objects of enquiry into two types – relations of ideas and matters of fact.
- Relations of ideas are analytic truths. As such, they are necessarily true, and can be known a priori
(deductively) and with certainty.
- Matters of fact are synthetic truths. As such, they are only contingently true, and can only be known
a posteriori (inductively), without certainty.
- So, Hume’s empiricism about knowledge is that:
 The only truths that we can know independently of experience are analytic truths (i.e.
relations of ideas – trivial tautologies that tell us nothing about the world and what exists).
 All substantive (synthetic) truths about the world, and what exists in it, must be known by
experience.
 So, all synthetic knowledge is a posteriori and all a priori knowledge is merely analytic.
Strengths of Hume’s empiricism:
- It is supported by the plausible scientific idea that we need to use observation and experiment to
find out about the world outside of us.
- It explains how we acquire some knowledge independently of experience, by saying that all such
knowledge is about things which are internal to us (namely; ideas).
- It explains why there always seem to be problems with a priori arguments for substantive truths
about the world (e.g. the ontological argument, the trademark argument, Plato’s arguments for the
Forms, arguments for the existence of the soul, etc.)
4. Issues with knowledge empiricism
4.1 Arguments against knowledge empiricism: the limits of empirical knowledge (Descartes’ sceptical
arguments.
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As our synthetic knowledge is acquired solely a posteriori, through a process of induction
and generalising from experiences (for example, the sun has risen in the past so the sun will
rise in the future) it is not certain. Because this knowledge is not certain it can be challenged
by scepticism.
While we may be certain that we are having sensory impressions we cannot be certain in
moving from these impressions to beliefs about the world.
Descartes highlights the uncertainty of information gained through the senses in the
sceptical argument he uses within his Meditations.
Using his ‘three waves of doubt’ he attempts to doubt all of his beliefs in order to find a set
of infallible beliefs from which to build a system of certain knowledge.
‘Some years ago I was struck by how many false things I had believed, and by how doubtful was the structure
of beliefs that I had based on them. I realised that if I wanted to establish anything in the sciences that was
stable and likely to last, I needed – just once in my life – to demolish everything completely and start again
from the foundations.’
Descartes, Meditations on First Philosophy, Meditation 1.
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Descartes’ first wave of doubt (the argument from illusion) involves him doubting his senses
because they have fooled him before. For example, he might believe he sees a friend walking
on the other side of the road, only then to find out it wasn’t actually his friend. However, he
realises that under normal conditions (for example up close and in normal lighting) he can
trust his senses.
His second wave of doubt (the argument from dreaming) involves him doubting his senses
because he could be dreaming. He argues that while he is experiencing sitting in front of a fire
writing a book, he has often dreamed about this, so how can he tell apart dreaming and
waking reality? However, he recognises that the materials of his dreams must be formed from
reality. Therefore, there must be a real external world from which the ideas in his dreams can
be built.
His third and final wave of doubt (the argument from the evil demon) involves him suggesting
that there could be an evil demon deceiving him about everything. This demon might trick
Descartes into believing there is an external world or of mathematical truths such as 2+2=4.
(The matrix is a contemporary example of the evil demon problem – that we are deceived
about the external world).
‘So I shall suppose that some malicious, powerful, cunning demon has done all he can to deceive me... I shall think that
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on FirstIPhilosophy,
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– ‘I think therefore
am.’ It is from
this belief1.

that Descartes builds his system of knowledge.
Thus Descartes critiques the empiricist ideology of knowing about the world through the
senses.

Additionally, if all knowledge of synthetic propositions can only be gained from sensory
experience then it would follow that to know that God or morality existed you would have to
have sensory experiences of God or morality and many argue that this is not possible.
4.2 Knowledge innatism (rationalism): there is at least some innate a priori knowledge (Plato and
Leibniz)
(a) Plato’s knowledge innatism:





Plato believes that we have immortal souls which before birth encounter the world of forms
– a realm of pure thought and perfect concepts in their pure state, for example ‘Beauty
itself’, ‘Justice itself’ and truths of mathematics and geometry.
When our souls are born into our bodies we forget most of these forms; however, through a
process of reasoning to prompt our memories we can access this innate knowledge in our
minds. Therefore, learning is a form of remembering.
The famous example Plato gives to demonstrate this is the dialogue between Socrates and
the slave boy in his Meno.
Socrates asks the slave boy a series of questions on a geometrical theory. Through the
discussion and the series of questions, Socrates draws out the answer from the slave boy.
Plato argues that the boy innately possessed this knowledge but it needed to be drawn out
through reason – Socrates’ questions triggered the knowledge the boy already possessed.
For Plato, this knowledge of the geometrical theorem could not have been acquired through
sense experience because as soon as we recognise the truth we realise that it has a universal
application (it does not just apply to one square but all squares); however, through the
senses we only ever experience particular examples of things.
 A criticism of Plato’s argument for innate ideas is that it rests on the metaphysical
assumption that a realm of forms exists and that we experience it before birth.
 A further criticism of Plato’s argument for innate ideas is that, in his slave boy example,
Socrates implicitly teaches the boy the geometrical theorem through his questioning and
thus his knowledge his acquired a posteriori and is not innate.
 Locke’s criticisms of innate knowledge: (As Locke defines an idea as any ‘immediate object
of perception, thought, or understanding’ also see section 2.3.2 on Locke’s criticisms of
innate ideas).
(i)
If there was innate knowledge then it would be universal. However, there is no
idea/piece of knowledge that is universally held. For example, ‘children and idiots’ do
not know the law of identity or the law of non-contradiction. Therefore, if no idea/piece
of knowledge is universal, no knowledge is innate.
(ii)
Locke argues that the most we can say is that the capacity for knowledge is innate. This
means that we are born with the ability to know things; however, this is not the same as
being born possessing innate knowledge. As Lacewing puts it, ‘the capacity to see
(vision) is innate, but that doesn’t mean that what we see is innate as well!’ (Philosophy
for AS, p.121).
(iii)
(iv)
If we have to ‘discover’ innate knowledge through reasoning, then how can we know it is
innate and not actually gained through experience?
Not everyone agrees on moral principles, so morality cannot be innate because if it was,
it would be self-evident to people.
(b) Leibniz’s knowledge innatism (responding to Locke):




Leibniz wrote his New Essays on Human Understanding as a response to Locke, arguing that
we do indeed possess innate knowledge.
Leibniz responds to Locke’s argument that there is no innate knowledge because there are
no universally held ideas (for example children don’t know the law of identity and the law of
non-contradiction) by arguing that children do possess this knowledge ‘without explicitly
attending to it’. So, whilst children cannot articulate this knowledge in words, they still
possess it and use this knowledge all of the time. Therefore, knowledge can be unconscious
– critiquing Locke’s claim that our minds are fully aware of all the ideas we possess.
Leibniz argues that all necessary truths are innate because experience is not able to give us
the knowledge of necessary truths. Leibniz does argue that sense experience might be
needed to trigger our innate knowledge; however, sense experience is not enough to give us
necessary knowledge. For example, we might gain knowledge of God through experience
and teaching but our knowledge of God as a necessary being goes further than this and
therefore must be known innately.
Leibniz responds to Locke’s claim that innate knowledge is only the capacity for knowledge
by arguing that, while innate knowledge is not ‘fully formed’ it is more than just a capacity
for knowledge. Innate knowledge exists as potential knowledge in our minds, needing to be
fully formed. An analogy Leibniz gives for this is a block of marble; ‘the veins of the marble
outline a shape that is in the marble before they are uncovered by the sculptor’ (New Essays
on Human Understanding).So innate knowledge exists as potential knowledge and
dispositions in the minds of humans that needs to be uncovered (through reason and
experience).
4.2.1 Knowledge empiricist arguments against knowledge innatism: alternative explanations (no
such knowledge, in fact based on experiences or merely analytic); Locke’s arguments against
innatism; its reliance on the non-natural.



Alternative explanations:
- Empiricists argue that necessary truths such as 2+2=4 are a priori but analytic. They argue
that we acquire the concept from experiencing, and then, in understanding the concept, we
come to know necessary truths. Therefore these truths (or the potential knowledge of these
truths) do not need to exist already in the mind.
- While it is easier to show how the truths of logic and mathematics are analytic, it is more
difficult for moral truths. However, Locke argues that moral truths are analytic and can be
deduced from other analytic truths. On the other hand, Hume argues that there is no moral
knowledge because moral claims are actually just expressions of emotions and feelings; they
cannot be true or false because they are not propositions.
Locke’s arguments against innatism (see above).
Innate knowledge’s reliance on the non-natural:
- Plato’s argument that the mind/soul exists before birth in the realm of the forms.
- Leibniz’s theory depended on the existence of a God.
- Descartes argued that our innate knowledge depends on it being planted there by God.
- All three philosophers appeal to God and the supernatural to explain why they think we
have innate knowledge. Innate knowledge therefore requires a more complicated
explanation for its existence than knowledge acquired through experience, and thus could
be objected to by using Occam’s razor.
- However, some modern philosophers have argued that we possess this innate knowledge
due to evolution and therefore there is no need to appeal to the supernatural.
4.3 Intuition and deduction thesis (rationalism): we can gain synthetic a priori knowledge through
intuition and deduction (Descartes on the existence of the self, God and the external world).

Empiricists claim that all knowledge of synthetic propositions is a posteriori, while all a priori
knowledge is of analytic propositions. So, anything we know that is not true by definition or
logic alone, we must learn and test through the senses.

Rationalists deny this, claiming that there is some a priori knowledge of synthetic
propositions.
 According to rationalists there are two key ways in which we gain such knowledge:
(i)
The knowledge is innate (already in our minds at birth). (This was discussed in section
4.2)
(ii)
Rational ‘intuition’ and deduction together help us to acquire certain truths
intellectually.
We will now be focussing on (ii).



Rationalists argue that we can deduce synthetic knowledge about the world from our
rational intuition a priori (without experiencing/observing the world).
Rational intuition involves discovering the truth of a claim just by thinking about it.
Descartes argued that we can establish knowledge of the existence of the self, God and
physical objects through rational intuition and deduction.
(a) Descartes on the existence of the self.
- After using his three waves of doubt, Descartes concluded that ‘cogito ergo sum’ – ‘I
think therefore I am’ – was the only piece of knowledge he could be certain of. He
thought this because, even if he doubts his own existence, he is still thinking and thus he
cannot doubt that a thinking thing exists:
‘he [the evil demon] will never bring it about that I am nothing while I think I am something.’
- From this truth, Descartes hope to build his system of infallible beliefs.
Descartes, Meditations on First Philosophy, Meditation II.
- At this point, Descartes does not know whether or not he has a body; he can only know
that he is a thinking thing:
‘a thing that doubts, understands, affirms, denies, wants, refuses, and also imagines and senses’
Descartes, Meditations on First Philosophy, Meditation II.
- Descartes knows what type of thought he is engaging in; for example ‘affirming’,
‘sensing’, ‘imagining’, etc. and he cannot be wrong about this – he can’t mistakenly think
he is affirming when he is actually imagining.
- Descartes defines his idea of the cogito (the existence of a thinking thing) as clear and
distinct.
- He then argues that, whatever he can perceive clearly and distinctly is true.
- Descartes defines a clear idea as: ‘ present and accessible to the attentive mind – just
as we say that we see something clearly when it is present to the eye’s gaze and
stimulates it with a sufficient degree of strength and accessibility.’
- He defines a distinct idea as: ‘so sharply separated from all other ideas that every part
of it is clear.’
- For Descartes, our rational intuition is knowing that clear and distinct ideas are true.
- Therefore, Descartes has shown how, through a process of rational intuition and
deduction, he can know the synthetic truth that the self exists.
-However, Descartes questions that, while we must consider that a clear and distinct
thought is true when we consider it, how do we know that it is true when we are not
focussing on it?
- In order to know whether clear and distinct thoughts are true when we are not
focussing on them, Descartes argued that we need to know that we are not being
deceived by God or an evil demon.
- Therefore, Descartes sets out to prove that we are not being deceived in order to
establish the truthfulness of clear and distinct ideas and, from that, the existence of an
external world.
(b) Descartes on the existence of God.
- Descartes offers two a priori arguments to prove the existence of God: His Trademark
Argument and his Ontological argument.
- Both of these arguments move from an idea of an omnipotent and perfect being to the
existence of this being.
- In addition to proving God’s existence, Descartes needs to show that this God would
not let us be deceived.
- It is a clear and distinct idea that God’s perfection is not compatible with deception.
- Therefore, God would not deceive us or let us be deceived by an evil demon.
(c) Descartes on the existence of the external world.
- Descartes argues that he has a clear and distinct idea of what a physical object is.
- He also argues that his perceptions of physical objects are involuntary and ‘much more
lively and vivid’ than imagination or memory.
- As his perceptions are involuntary they cannot be caused by himself (otherwise he
would know about the cause of them) so they must be caused by something external to
him.
- As God exists and is perfect and not a deceiver, Descartes’ perception of physical
objects must be caused by physical objects themselves.
- Therefore, there is an external world of physical objects causing our perceptual
experiences.
Therefore, according to Descartes, he is able to prove the existence of the self, God and an external
world through a process of rational intuition and deduction rather than sensory experience.
(d) Geometry

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
Geometry is another proposed example of how we can gain substantive knowledge of the
world independently of the senses.
For example, the Greek mathematician Euclid started with a set of self-evident axioms and
definitions (e.g. All right angles equal each other) and moved from these to prove a further
set of propositions.
Through the careful use of reason, Euclid was able to establish a large and systematic body
of truths all derived from his initial axioms and definitions.
It is argued that the truths established through reason are synthetic rather than merely
analytic because they can be applied to the world (for example we are able to construct
buildings and bridges using geometrical propositions).
Geometry seems to be telling us new facts about the nature of physical space, facts that
have genuine application and are not just true by definition.
4.3.1 Knowledge empiricist arguments against the intuition and deduction thesis:

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

Mathematical and geometrical knowledge is a priori but analytic (rather than synthetic)
according to the knowledge empiricist – in order to know mathematical truths we simply
need to analyse the concepts involved.
Additionally, if the mathematical/geometrical initial assumptions are derived from
experience, then the whole system is grounded in experience anyway and we are not
gaining any new knowledge a priori.
Descartes has not managed to prove that he knows he is a thinking thing; it could be argued
that there is simply a collection and succession of thoughts, but there needn’t be any single
thing that persists between these thoughts. Perhaps Descartes should say ‘thoughts exist’
rather than assuming a self behind these thoughts.
Empiricists might also argue that Descartes’ knowledge that a thinking thing exists isn’t
synthetic knowledge because it derives solely from our knowledge of ourselves and the
debate between the rationalists and empiricists centres on synthetic knowledge of the world
outside one’s mind.
Descartes’ arguments for the existence of God have also been strongly critiqued (see section
2.2.1 of The Definition of Knowledge section for criticisms of Descartes’ Trademark
Argument and see Philosophy of Religion notes for criticisms of Descartes’ Ontological
Argument).
Descartes’ argument for the existence of physical objects and the external world depends
upon the existence of God. Therefore, if his arguments for the existence of God fail, then so
too does his argument for the existence of an external world.
Descartes’ arguments for God and physical objects have also been criticised for being circular –
known as, ‘The Cartesian Circle’. Descartes relies on clear and distinct ideas in order to prove the
existence of God; however, he relies on the existence of God to know that clear and distinct ideas
are true (that he is not being deceived).