trcr · Web view2018/01/06 · Complete reliance on how the world is. If the world were different, it wouldn’t be true (called contingently true) Is the opposite conceivable? No

SYNTHETIC KNOWLEDGENote: Before reading this handout, you must have read and fully understood the sheet of key terms.

Remember: by “knowledge”, we mean claims or propositions such as “Paris is the capital of France”, “it is raining outside” or “all triangles have three sides”.Make sure you are clear about the difference between knowledge like this and concepts (like “France”, “rain” or “triangles”).

KNOWLEDGE EMPIRICISMThe claim that all synthetic knowledge is a posteriori and all a priori

knowledge is (merely) analytical.

Hume’s Fork

Hume’s Fork is the name given to a distinction Hume draws between different kinds of knowledge.

“All the objects of human reason or enquiry fall naturally into two kinds, namely relations of ideas and matters of fact.”

By this, Hume means that there are two types of knowledge. All knowledge is either a “relation of ideas” or a “matter of fact”. He claims that any proposition which is neither of these is meaningless.

Matters of Fact are facts about the world and we gain this kind of knowledge through our sense experience. This sense experience might be direct (I look out the window to know that it is raining) or indirect (I read in a book that the battle of Hastings happened in 1066).

Relations of Ideas are the kinds of knowledge claims we use in maths (2+3=5) or in logic (something cannot exist and not exist at the same time). We do not gain this knowledge through sense experience, but through reason (just thinking about the concepts involved).

Epistemology 6: Synthetic KnowledgePage 1

The main differences between these two kinds of knowledge are outlined below:

Relations of Ideas Matters of FactCovers Mathematics,

geometry, logicFacts, generalisations about the world

Examples 2 + 4 =6.All triangles have three sides.

Barack Obama was a US president.Water can turn into ice.

Certainty Level Absolute Less than 100%How we know By thinking alone

(called a priori)By experience (called a posteriori)

Reliance on how the world is

None. Would be true in all possible worlds. (called necessarily true)

Complete reliance on how the world is. If the world were different, it wouldn’t be true (called contingently true)

Is the opposite conceivable?

No. It is true by definition (called an analytic truth)

Yes, the opposite is conceivable and possible (called a contingent truth)

So, Hume is claiming that all synthetic knowledge is a posteriori. This means that we get knowledge about the world by experiencing the world. He is also claiming that all a priori knowledge is analytic. This means that there is some knowledge that we acquire without any sense experience, based on the terms involved. But it doesn’t tell us anything new about the world.This view is known as knowledge empiricism.

Opponents of empiricism claim that there is some a priori knowledge which is synthetic. This means that there is new knowledge about the world that we can gain without the need for any sense experience. Since it isn’t gained by sense experience, it either must be gained through reason (rationalism) or it is innate (knowledge innatism).


KNOWLEDGE INNATISM There is at least some innate a priori knowledge

Knowledge innatists claim that we can have synthetic a priori knowledge about the world. This means we can have knowledge gained by reason, not by the senses, which is substantial and not just true by definition.

Plato – Mathematical knowledge is innate

Plato argues that learning is just remembering things that we already have knowledge of, we just don’t realise it. He uses the example of mathematical or geometrical knowledge. Socrates asks Meno’s slave boy (who has never been taught geometry) a series of questions, leading him to figure out a geometrical theorem.Since the boy’s knowledge did not come from experience, it must have been innate. And

since it is not true simply by definition, it must also be synthetic.


Another example from geometry is the work of another ancient Greek- Euclid. Euclid was a mathematician who established the foundations of geometry. It was a set of basic principles which were held to be self-evident and which couldn’t be doubted.

Examples of Euclid’s principles include:

Parallel lines never meet each other.

Every point on a circle is the same distance from the centre.

Because these propositions seem so obviously true, and everyone would agree with them, it can be argued that these are examples of innate, a priori knowledge. Since once again some would argue that we cannot establish these proposition simply by looking at the definitions, these statements would also be considered synthetic,

Leibniz – All a priori truths are necessary and innate

Leibniz argued that there can be innate synthetic knowledge that we have, but are unaware of.

An example is the claim “It is impossible for the same thing to both be and not be”.

This is knowledge not true by definition (synthetic) that we can know just through thinking (a priori). Everyone uses this knowledge all the time (when it comes to identifying the differences between things in the world), but without really being aware of it:

“Even if we give no thought to them, they are necessary for thought. The mind relies on these principles constantly.”

In fact, Leibniz goes as far as arguing that all a priori knowledge is innate.


Because we can work it out just by using our mind, it must have been there in our minds all along. That is, it must be innate.

Leibniz argues that we come to know these innate truths by “attending to what is already in our minds”, and he cites Plato’s Meno as an example of this.

KNOWLEDGE EMPIRICIST ARGUMENTS AGAINST KNOWLEDGE INNATISM

To prove the innatist wrong, the empiricist needs to explain how these examples of synthetic knowledge could have come about if they are not innate.

“Innate knowledge” is not really knowledge

One way to do this is to argue that it is not really knowledge. For example, although Euclid’s principles of geometry seem to be true in all cases, the work of Einstein and others now suggests that this is not the case. The real world may not be Euclidean, so in reality, parallel lines do meet, just not in a way that can be observed by the human eye.

If Euclid’s principles are not actually true, then they are not knowledge (given the usual definition). So they are not an example of innate synthetic knowledge.

Parallel lines in non-Euclidean space:

“Innate knowledge” is actually a posteriori


The empiricist could respond to suggestions of innate knowledge by claiming that these examples are gained not by reason, but by sense experience.For instance, the slave boy was basing his knowledge on his experience of squares. And Euclid knew that parallel lines don’t meet because of his experience of parallel lines.

Some philosophers, such as Mill, have argued that all mathematical knowledge is actually based on experience. For instance, I know that 2 + 3 = 5 because I have seen 2 things and 3 things, and when I put them together I have seen that they make 5.Mill claims that there is no a priori knowledge. All knowledge is a posteriori. If sense experience is required to know these propositions, then they are not innate or a priori.

“Innate knowledge” is actually analytic

Another way the empiricist can respond is to claim that these proposed “innate” propositions are only analytically true. They are true just because of the meanings of the words, so they tell us nothing new about the world.

For instance, it is part of the definition of parallel lines that they don’t meet. Similarly, if you know the definition of the word “circle”, then you automatically know that all the points are the same distance from the centre. This claim isn’t separate from the definition itself.

For Leibniz’s example of “the same thing can’t both be and not be”, again if you understand all the words in this sentence, then you know that the claim is true. This truth isn’t something separate from the definitions in the sentence.

If these truths are not synthetic but analytic, then the innatist has failed to prove that there is innate synthetic knowledge.

Locke’s arguments against innatism


Locke gave several arguments against the idea of innate knowledge in general, using common examples such as “It is impossible for the same thing both to be and to not be”.

1. His first point is the same one he made about innate concepts - No proposition is known universally (“children and idiots” do not understand them, so they can’t know them). If it isn’t universal, then it isn’t innate.

The innatist can respond by claiming that innate knowledge doesn’t require that everyone actually knows it, but that everyone would know it they used their reason correctly to work it out. Locke responds by asking, if it really is innate, so we already have it, then why do we need reason to discover it?

2. The innatist might claim that innate knowledge is “self-evident”. That is, we agree that it is true as soon as we think of it. But Locke thinks this seems to be the case for lots of knowledge that is not innate. For example, “white is not black” is self-evident. But our knowledge of it seems a posteriori (based on sense experience). Just being self-evident does not automatically make something innate.

3. Locke’s final argument against the innatist is that for innate knowledge to be possible, the concepts it is based on must be innate. If they are not innate it means any knowledge built on them has its roots in our experience, meaning we’d surely say it’s a posteriori. Since he believes he has proved innate concepts to be impossible (see previous handout), innate knowledge cannot be possible.

Reliance on the non-natural


One final problem for the innatist is, if knowledge doesn’t come from sense experience, where does it come from?

Plato’s answer is that the non-physical mind existed, containing this knowledge, before birth. Leibniz and Descartes argue that innate knowledge must come from God.

If we don’t accept these non-natural explanations, then it doesn’t seem like we can accept the existence of innate knowledge.

Some modern philosophers have appealed to natural explanations, such as evolution, as an explanation. While this appears to work for certain knowledge claims, such as “physical objects exist” or “beings with other minds exist”, it is difficult to see how we could evolve to have knowledge of geometry or maths.

RATIONALISMWe can gain synthetic a priori knowledge through intuition and deduction


Like knowledge innatists, rationalists claim that we can have real new knowledge about the world that is not based on sense experience (synthetic, a priori knowledge). But rather than it being present in everyone at or before birth, we can come to know it by using our powers of reason.

Intuition and Deduction Thesis

Rational intuition means the ability to understand something just by thinking about it.

Deduction means figuring out what must follow from certain claims. So, once you accept one claim as being true, deduction is the ability to move from that to other true claims, just by thinking about them.

Intuition and Deduction Thesis is the theory that we can gain substantial knowledge by using our rational intuition and/or deduction (that is, we can gain knowledge just by thinking).Philosophers who accept the intuition and deduction thesis are known as rationalists.

The main rationalist philosopher is Descartes, and we’ll now look at his main ideas in detail:

Important Note: Whilst we will attempt to apply the definitions we’ve used throughout this topic to Descartes work, it’s worth noting he was writing before distinctions such as A Priori, A Posteriori, Analytic and Synthetic had been outlined philosophically. Thus there is some debate about where his ideas actually fall. Regardless, he certainly believed there were things he could know about the world just by thinking.

Descartes’ doubt

In the Meditations Descartes places all his previous knowledge in doubt in order to find a secure foundation which can’t be doubted. Descartes’ doubt comes in three waves.

First, the reliability of the senses as a source of knowledge is rejected because of illusions and hallucinations. Then he employs the argument


from dreaming to suggest that even his ability to tell the difference between reality and illusion could be compromised (because we could be dreaming and we wouldn’t know). Finally he imagines that an evil demon is deceiving him about everything, even about mathematical truths. Since all these things could be affecting him, everything he thinks he knows is in doubt.

A priori knowledge of the self

Having pushed this method of doubt to its ultimate limits, Descartes now sees that there is at least one truth which cannot be doubted. He reasoned that if he was doubting everything, he could be sure of one thing: that he existed. For, if he was doubting, he must exist in order to doubt. Going further, doubting is a form of thinking, so he must exist in order to think.

“Cogito ergo sum”; I think, therefore I am.

He now has certain, undoubtable knowledge of his own existence. This knowledge is not derived from any

kind of sense experience, but on his own reason and deduction.

“If there is a deceiving demon then ‘I too undoubtedly exist, if he is deceiving me. Let him deceive me as much as he can, he will never bring it about that I am nothing, so long as I think I am something.’

Hence, ‘I am, I exist’ is necessarily true whenever it is put forward by me or conceived in my mind.”

Having established his existence, Descartes now proceeds to investigate his nature or essence – what type of thing is he? He is not essentially a physical being, for, applying the method of doubt, he can doubt his own body – or indeed whether any external objects exist. The only attributes which he cannot deny of himself are mental ones, and hence he concludes that:

‘I am a substance whose whole nature or essence is to think and whose being requires no place and depends on no material thing’.


Clear and Distinct Ideas

From this one item of certain knowledge (i.e. the cogito), he derives a criterion of certainty- what Descartes calls clear and distinct ideas:

Knowledge of oneself is clear and distinct, self-evident. Generalising from this, Descartes concludes that whatever is clear and distinct is true and cannot be doubted: it is knowledge.

These clear and distinct ideas have nothing to do with the perceptions of the senses; instead they are purely intellectual like the basic, self-evident propositions of mathematics and logic.

A priori knowledge of God

He thinks that the existence of God is a clear and distinct idea, or is deduced from ideas that are clear and distinct. He gives a number of arguments supporting this claim, but the most common is his ‘trademark argument’. While he is aware of his own imperfections, he is also aware that he has within himself the idea of a supremely perfect being. Descartes reasons that this idea must have been placed in him by a really existing perfect being – God (see the trademark argument in handout E5).

So when the question arises, “How do you know that a demon is not deceiving you into thinking that whatever is clear and distinct is always true?,” from now on Descartes can answer that God, being good and all powerful, would not allow him to be so deceived.

From God to the World

But do bodies – do physical objects – exist? Of course, we might say: they cause our experiences. But Descartes has argued that we don’t yet know what causes our experiences – it could be a demon or


supercomputer. Descartes later argues that there are only three options for what might cause these experiences: a real external world of physical objects, a demon, or God.

1. If the cause was God, this would mean that God was a deceiver because He would have created us with a very strong tendency to believe something false (viz. that a physical world exists).

2. if it was a demon, then if God exists, God is as good as a deceiver, since God is allowing the demon to deceive us.

However, Descartes argues, God is perfect by definition. Because we know that God is perfect, we know that God is not a deceiver. So if God exists (see arguments above), then there must really be an external world.

A priori knowledge of the external world

Finally when it comes what we know of the world, Descartes decides to apply his new method of ignoring the senses and relying on a priori, clear and distinct ideas. He gives the example of a piece of wax:

‘Let us take, for example, this piece of wax. It has just been taken from the

honeycomb; it has not yet quite lost the taste of the honey; it retains some of the scent of the flowers from which it was gathered; its colour, shape and

size are plain to see; it is hard, cold and can be handled without difficulty; if you rap it with your knuckle it emits a sound … But even as I speak, I put the wax by

the fire and look: the residual taste is eliminated, the smell goes away, the colour changes, the shape is lost, the size increases; it becomes liquid and

hot, and if you strike it it no longer emits a sound…

… So what was it in the wax which I understood with such distinctness? Evidently none of the properties arrived at by means of the senses’.


So, the perceivable properties of the wax give us no real knowledge about the wax itself. The only essential property of the wax is its extension: it is simply an extended thing which has length, breadth and depth (although these dimensions can change). But this is not something we perceive via the senses or the imagination, for we know the wax is capable of taking on many more shapes than we can ever actually observe or picture to ourselves.

Descartes’ argument here goes like this:

1. My sense experience of the wax changes. Nothing I can sense is the same.

2. I know it is the same piece of wax.

3. Therefore, my knowledge of the wax is not based on my sense experience, but on deduction.

So Descartes concludes that ‘we know that bodies are not strictly perceived by the senses or by the faculty of imagination but by the intellect alone’.

So, Descartes has used pure reason (intuition and deduction) to come to know three propositions: that he exists, that God exists and that the external world exists in an extended form.

He has gained this knowledge without any use of his senses, so it is a priori. But it does tell him meaningful new information about the world, so it is synthetic.


KNOWLEDGE EMPIRICIST ARGUMENTS AGAINST INTUITION AND DEDUCTION

There are two main criticisms of Descartes’ rationalism: The first is that his conclusions do not really follow from his

reasoning. The second is that even if his conclusions did follow, they are not

meaningful.

The ‘Cartesian circle’

A major problem with Descartes’ argument is that it relies on circular reasoning:

We cannot trust our clear and distinct perceptions until we know that God exists; but we cannot prove God exists without relying on our clear and distinct perceptions.

Descartes’ answer to this notorious problem (known as the ‘Cartesian circle’) appears to be that there are some propositions which are so clear and distinct that, even without relying on God, they are self-guaranteeing. ‘Two plus two equals four’ or ‘if I think, I exist’ are such simple and straightforward propositions that I cannot possibly be mistaken as to their truth.

Tautology (analytic truths)

The difficulty for Descartes, however, is that such tautologous or near-tautologous propositions give us very little information. The knowledge he can establish without relying on circular reasoning is merely analytic: it merely tells us the meaning of the words within the proposition.


But as soon as we want to go further, to establish more substantial claims about the existence of God or the nature of the universe, then it seems that we are moving beyond these self-evident truths. Since they are not self-evident and we can’t rely on circular reasoning, we can’t really know that they are true.

So, Descartes seems to face a fatal dilemma. Either his knowledge begins and ends with thin and unexciting propositions such as ‘two plus two equals four’ or ‘if I am thinking, I exist’, which buy their truth at the cost of being relatively uninformative; or else it advances to more important and substantive truths at the cost of losing the kind of certainty and necessity which he was originally looking for.

ARGUMENTS AGAINST KNOWLEDGE EMPIRICISM

The limits of empirical knowledge

However much we may doubt Descartes’ rationalist argument for a priori synthetic knowledge, his sceptical argument about the reliability of the senses raises important issues with knowledge empiricism. If our senses can be easily deceived (by illusions, hallucinations etc.) then how can they give us accurate knowledge of the world? But much of what we consider to be knowledge does not derive from the senses.

Empiricists deny that there is any a priori knowledge of synthetic propositions. It follows from this that any claim that is neither analytic nor known a posteriori, we do not know. However this rules out many claims that we like think we do know. For instance it appears to show that we cannot know that physical objects exist – which few people would agree with. If we don’t want to rule out this type of knowledge, then we must admit that empiricism is false. Consider:

1. (According to empiricism) All knowledge of synthetic propositions is a posteriori

2. ‘Physical objects exist’ is a synthetic proposition3. But we cannot know, through senses experience, that physical

objects exist.4. Therefore, (according to empiricism) we cannot know that

physical objects exist.


5. Therefore, either we cannot know that physical objects exist, or empiricism is false.

6. But we can know that physical objects exist7. Therefore empiricism is false.

Morality

Moreover, this argument can be adapted to generate objections to empiricism in other areas of knowledge, for example morality. Moral claims, such as ‘murder is wrong’, don’t appear to be analytic. But could we know them through sense experience? Which of our senses pick up on ‘wrongness’, and how? If empiricists can’t show that moral claims are either analytic or a posteriori, then they will be forced to conclude that there is no moral knowledge.

Science

Another problem area for empiricists is science. Scientific knowledge is based on the assumption that because certain events have always happened in the same way in the past, they will in the future. Our sense experience can give us knowledge that a chemical behaved in a certain way yesterday, and the day before, and when a colleague did the same experiment 2 years ago. Although it is highly probable that it will happen this way on future occasions, it is not guaranteed. This is known as the problem of induction. Inductive reasoning is the basis for scientific knowledge, and yet it doesn’t come from the senses. So either it is not knowledge, according to empiricism, or empiricism is false.

Relying on sense experience

If knowledge empiricism is to work, it needs to be based on a reliable theory of perception. We have already seen that the debate about perception is far from over. So, it seems that our senses cannot give us certain knowledge of anything.

Final Thoughts…

Is all synthetic knowledge a posteriori?

Or is some synthetic knowledge innate?

Or can we gain synthetic knowledge through reason?


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trcr · Web view2018/01/06 · Complete reliance on how the world is. If the world were different, it wouldn’t be true (called contingently true) Is the opposite conceivable? No