Kant

Kant’s Synthesis 

‘Thoughts without content are empty, intuitions without concepts are blind.’

With this thought, Kant attempts to bring together the apparently opposed ideas of empiricism and rationalism. He synthesises their views in the claim that empiricism was right to say that experience, in the form of sensory perception (intuitions to Kant) is essential to knowledge, but the rationalists were right to say that the mind’s ‘rational’ structures make our understanding of those sensory perceptions possible by imposing the (‘pure intuitions’ of time and space and the ‘categories’ of: 

quantity: (unity, plurality and totality); 

quality: (reality, negation, limitation); 

relation: (inherence and subsistence, causality and dependence, and reprocity): 

modality: (possibility and impossibility, existence and nonexistence, and necessity and contingency) 

Without these organising structures experience itself would not be possible. We are so built, he thinks, that we have to experience the world outside ourselves as spatial and temporal (flowing through time) not because the outer world is spatial and temporal, but because we impose spatiality and temporality on the 'intuitions' we have of it.

Copernican Turn

It is in this sense that Kant’s philosophy represents a ‘Copernican turn’, rather than the world somehow imposing understanding of itself on our minds, our minds impose our understanding on the world - our minds give the the world the form we perceive it as having.

However, according to Kant, it is not the actual world 'in itself' that we perceive, this is beyond our perception; what we experience is the world of 'phenomena', the underlying reality behind the world we experience the world of 'noumena' is forever hidden to us. 

Kant’s Synthetic a Priori

Kant believed that claims about the world could be both 'synthetic' in that they could tell us something about the world that isn't contained in their own terms, and 'a priori' because they can be known independent of experience of the world. 

This is a response to Hume who had denied such a possibility. 'Hume's fork' (see previous entry) made a strict separation between synthetic propositions, which for him could only be known 'a posteriori' and 'analytic' propositions which could be known a priori, but told us nothing about the world that was not already contained in their terms. 

To understand this we have to look at the way the sentences we use to make propositions and claims about the world work. Sentences consist of subjects (the thing the sentence is about) and predicates (the words that say something about the subject). So, the sentence ‘Some frogs are green’ has ‘Some frogs’ as its subject and ‘are green’ as its predicate. 

Both Kant and Hume thought that 'analytic' statements are those in which the subject contains the predicate and consequently they don't add any information about the world: an example of this would be the sentence ‘green frogs are green’, or to push it a little further, 'kangaroos are animals', because we could claim that the concept of 'kangaroo' contains the concept of 'animal', so if we already have the concept of 'kangaroo' we already have the concept of 'animal' and we know this independent of (further) experience', we know it 'a priori'. 

On the other hand the predicates of 'synthetic' statements are not contained in the subject, so they do give us additional information about the world; for example ‘This frog is green’ or 'this kangaroo has a stamp collection.'

But Kant thought that statements like '7 + 5 = 12' were both 'synthetic' and 'a priori', in fact he thought that 'Mathematical judgments are all, without exception, synthetic.' For Kant, there is nothing contained in the concept of '7' and '5'  that makes the knowledge that adding them together will result in '12' immediately obvious or ineluctable. What he was getting at is perhaps easier to see if we consider larger numbers like for example, 38976 and 45204; their sum 84180 certainly does leap out at me, but I'm v. poor at maths. I think this gives an inkling of what Kant meant, but an awful lot of reading is really required to work your way into his idea. 

Kant also thought that science could come up with synthetic a priori statements. He claimed that the statement, 'In all changes in the physical world the quantity of matter remains unchanged.' was such an example; he said;

Now, in  thinking the concept of matter I do not think its permanence but only its presence in the space that it fills. Thinking that matter is permanent isn’t like thinking that women are female, or that tigers are animals. In judging that matter is permanent, therefore, I go beyond the concept of matter in order to add to it something that I didn’t think in it. So the proposition isn’t analytic but synthetic; yet it is thought a priori. He also claimed that the statement, 'When one body collides with another, action and reaction must always be equal' was synthetic and a priori. 

Again it is not obvious (not to most mortals anyway) exactly what he meant, but if we consider his ideas about the 'categories': how we experience the world in the way we do because time, space and cause and effect are built in to the way our minds are set up to experience the world, then we begin to see how we might know 'a priori' the stuff above about action and reaction, and such 'knowledge' certainly seems to add to our information about the world and is therefore 'synthetic'. Hume, of course denied that ideas about cause and effect, action and reaction etc. were anything other than the product of experience and as such, although synthetic, could only be known 'a posteriori'.

Causation is another example of synthetic a priori knowledge Kant claims that ‘Every event has a cause’ can be known a priori and is synthetic because it tells you something that isn’t contained in the terms: event is not synonymous with cause - depends how you think about it really!?:/ 

So, I hope that's clear, now. Another Saturday afternoon bites the dust of metaphysical speculation. 

Descartes, Locke & the Story of Epistemology

I wanted to remind you of the point of the stuff we'd looked at - why did Descartes bother to sit in his oven searching for certainty? What was the story? So we wrote  a little note that was similar to what follows except I've tried to improve and clarify it. And I've added a long rambling introduction. 

Descartes was working in a difficult period, (aren't we all?), he was very keen on the new scientific thinking or 'natural philosophy' as it was called, which had begun to question the dominant religious ideology of the time. It was only 100 years since Copernicus had rather upset the church by demonstrating the 'revolutionary' idea that the Earth revolved around the sun, thus shifting 'man' from the centre of the universe where God had apparently put him. 

Descartes himself was big on maths inventing Cartesian coordinates by which you can identify the precise spot at which a fly is located on a ceiling!  Anyway, he wanted to apply the new 'scientific' way of thinking to the most fundamental questions like 'is Scott right about the Matrix?'  He wanted to turn the rigour of rational thought inward and examine the contents of his mind. But we could also read his Meditations as a program for rebuilding society: Descartes wanted to sweep away superstition and received wisdom and replace it with rationally constructed principles.  He also wanted to show that he could prove a) the power of 'men' to use rational thought and b) that God existed. If he could use the power of rational thought to prove that God existed then he hoped the church might see the rational enquiring mind as less threatening and more helpful.

So, if Descartes was to challenge all the strange ideas of his time he had to have a strong foundation for his own knowledge claims. that foundation is of course provided by his 'cogito', and on this point of certainty that he 'grounds' his epistemology. The cogito is thus 'foundational'. 

Having established beyond any scepticism the certainty of his existence as a thinking thing, Descartes can claim epistemological grounds for his subsequent ideas about the nature of the physical world that he perceives through his senses, (like the wax) but knows and understands through his faculty of Reason.

John Locke, some 50 years later, rejects Descartesʼ ideas as to how to ground knowledge. For Locke the mind is a blank slate - a tabula rasa, and all the ideas, all the knowledge that we come to possess comes to us through our senses. 

This dispute sets up a philosophical debate that has, in various forms, rumbled on into contemporary philosophy. 

The argument can be summed up in basic terms as a dispute about how the kinds of things that seem to go on inside our heads relate to the kinds of things that seem to go on outside our heads. Do we have accurate representational knowledge of the world? Is that even a sensible question? 

Wax, wax, wax, always the ... wax !

Below is a revised, redrafted and extended (hurrah! they cry) version of the various notes I have written with you and last year's lot on this wax business. It's got quite long and I possibly repeat myself a little, but it has been useful to me to re-read and re-write it, so I hope it will help you.  I suppose it represents a kind of response to the wax essay question, but try not to rip me off too much. (You might be better off writing your response before you read it).

Anyway ...


Descartes’ ‘Meditations’ are an attempt to find the foundations of objective (certain and unchanging) knowledge. Descartes believes that if he can find an ‘Archimedian point’ - just one thing about which there can be no doubt then he will be able to ‘ground’ all his other ideas. It is an attempt to construct a complete epistemology - a theory of knowledge - by building, piece by piece (brick by brick) on his foundation of certainty. (The cogito)

Having found his one point of certainty, that he exists as a ‘thinking thing’ Descartes tries to work out the status of the ideas that run through this ‘thinking thing’ that he is. His problem is that most of his ideas seem to come through his senses and he has already shown these to be unreliable and deceiving.

He decides that this thinking thing is ‘a thing that doubts, perceives, affirms, denies, wills, does not will, that imagines also and which feels.’ These activities of the mind are the more certain the less they have to do with the physical world. Therefore the imagination, which seems to build its ideas from perceptions of the physical world is less trustworthy than, for example, the act of doubting, (Remember Descartes prefers geometry to geography for similar reasons.)


In his Second Meditation, having pushed his scepticism, his 'method of doubt', through arguments concerning illusion and dreams and on to the point of considering that a malignant demon might be feeding him illusions about the world, Descartes, finally arrives at his point of certainty, 'I am, I exist', he claims, and goes on to say that this 'must be true whenever I assert it or think it.' To be thinking the thought of one's existence is, in itself, proof of that existence, he says.


Although Descartes is now certain of his existence as a mental entity he is still in doubt about the thoughts and ideas that he has as a thinking thing. (where do they come from? how trustworthy are they? are some more trustworthy than others?) He thinks again about the ideas that seem to come to him through the senses and begins to reconsider the physical world and the way he perceives it in order to understand how it is that he can be certain about his mental existence, but in doubt about the physical world.


In a famous passage he considers the way his senses give him perceptions of a piece of wax, and how those perceptions are utterly different and distinct depending on whether the wax is hard or melted. He concludes that although we normally understand our senses as providing us with understanding: to 'see' something is to understand it we believe, the example of the wax shows Descartes that 'Something that I thought I saw with my eyes ... was really grasped solely by my mind’s faculty of judgment.


Descartes discussion of the wax is central to understanding his notion of what it is to be a human being. It is his ability to conceive (have a concept of) the wax that, for him, demonstrates the power of rational thought. He concludes that because the information given to him by his senses about the wax is insufficient to allow him to know that the wax remains the same thing after it changes all its sensible qualities, it must therefore be his 'reason', his faculty of judgement that gives him knowledge of the wax. It is as if through the power of rational thought the sum of his understanding is greater than the understanding his senses alone could provide. This 'added power' provided by ‘reason’ is the underlying principle of Rationalist philosophy.


Descartes believes that knowledge of the external world is gained through the mind’s understanding (judgement) of the information we receive through the senses. The faculty of judgement is a mental capacity (ability) that brings together the ‘raw’ and potentially incoherent information of the senses and allows us to understand.  This makes him a rationalist as opposed to an empiricist. (we're doing them next).


For Descartes, this wax business confirms his belief that, he can know his internal world - his mental processes - better and more certainly than he can the external physical world. This emphasises the separation and the difference of the two ‘stuffs’ mental and physical and makes clear his ‘dualism’.