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Hume s Fork

Hume's Fork v Section II. Section II divided up

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Hume s Fork

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    1. Hume’s Fork

    2. Hume’s Fork v Section II Section II divided up ‘the perceptions of the mind’ (2.1) into impressions and ideas. The start of Section IV (4.1-2) introduces us to what has become known as Hume’s Fork (this is not a phrase that Hume used). It divides up ‘all the objects of human reason or enquiry’ (4.1)

    3. The perceptions of the mind V All the objects of human reason or enquiry What, therefore, is the difference between these two divisions? It is not clear how Hume saw the relationship between the two, and, for your purposes, it would be safest to treat them as two completely independent operations, even if some of the data overlaps. Make sure that you do not make the common mistake of confusing the two divisions that Hume makes.

    4. The perceptions of the mind V All the objects of human reason or enquiry Learn them as follows: Section II divides up all the contents of the mind. Hume’s Fork divides up all our knowledge. That is, everything that we know belongs to one of two categories. The focus has changed from that of Section II and Section IV as a whole (not just the Fork) can be read completely independently of the earlier chapters.

    5. Hume’s Fork has only 2 Prongs In one sense, you only have to learn one of the 2 prongs because, basically, Hume defines all items of knowledge as follows: Prong 1: Each Item is of Type X; Prong 2: Or it is not of Type X. This may seem trivial but it will be important to bear this in mind when we consider a common criticism of the Fork later.

    6. Thus …

    7. ‘Type X’ and ‘Not-Type X’ The table on the previous slide made it clear how Hume defines the two categories in relation to each other. It is worth stressing this point again, though, because many students give positive descriptions of ‘Matters of Fact’ (Prong 2), rather than defining it more negatively as the opposite of Prong 1. You will already have recognised the distinction that Hume makes with his Fork because it has become a common one in modern philosophy, e.g. the difference between analytic and synthetic expressions. You have learnt that synthetic expressions are a posteriori, i.e. they are dependent on experience. So it is tempting to go along with many other students and to say that items of knowledge from Prong 2 are learnt by experience. But this would be wrong for 2 reasons …

    8. 1st Reason for not saying ‘Experience’: (1) When Hume introduces his Fork at the start of Section IV, he does not say that matters of fact are learnt by experience – at least, not yet. Much of Section IV is given over to the question of how we come to learn ‘matters of fact’. All he says initially is that they are not learnt by mere thought. To state that we learn them by experience would be prejudging the issue at this point. As you quickly scan through the following paragraph about matters of fact, you will notice that nowhere is experience mentioned : Matters of fact, which are the second objects of human reason, are not ascertained in the same manner; nor is our evidence of their truth, however great, of a like nature with the foregoing. The contrary of every matter of fact is still possible; because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness, as if ever so conformable to reality. That the sun will not rise to-morrow is no less intelligible a proposition, and implies no more contradiction than the affirmation, that it will rise. We should in vain, therefore, attempt to demonstrate its falsehood. Were it demonstratively false, it would imply a contradiction, and could never be distinctly conceived by the mind. [4.2]

    9. 2nd Reason for not saying ‘Experience’: (2) While Hume does actually think that we learn about matters of fact through experience, we shall see that in Part 2 of Section IV he adds an incredibly important qualification to this.

    10. Relations of Ideas Hume links relations of ideas to Geometry, Algebra, and Arithmetic; His examples are mathematical: (Example 1) That the square of the hypothenuse [Scottish spelling?] is equal to the square of the two sides; (Example 2) That three times five is equal to the half of thirty. Few students appreciate why Hume chose the labels that he did (R of I and M of F), but they are both very appropriate. Hume gives an indication of why he chose relation of ideas when discussing the above examples: example 1 expresses a relation(ship) between the figures involved, and example 2 between the numbers involved. In other words, Maths involve expressions that include two ideas that we are already familiar with and the knowledge / Maths part comes when we notice the relationship between these two ideas.

    11. Relations of Ideas Here’s my example: Mathematical concept 1: an equilateral triangle is one that has 3 equal length sides; Mathematical concept 2: a rhombus has 4 equal length sides. Therefore, I intuitively notice that 2 equal-sized equilateral triangles can be used to make a rhombus:

    12. Relations of Ideas An important part of Hume’s definition of relations of ideas is that they “are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe.” [4.1] Hume stresses the point by saying that even if “there never were a circle or triangle in nature, the truths demonstrated by Euclid [a geometrician] would for ever retain their certainty and evidence.” [4.1] The complete independence of relations of ideas from the real world is what makes it possible for us to discover them just by thinking.

    13. Matters of Fact As we have noted many times, these are defined negatively at the start of Section IV. The main focus of Hume’s opening description is to say that the opposite of a matter of fact is possible and conceivable – Hume stresses this because this is not the case with relations of ideas.

    14. Matters of Fact He notes that the following two phrases are equally intelligible – neither implies a contradiction: (1) The sun will rise tomorrow; (2) The sun will not rise tomorrow; By contrast, this does not work with relations of ideas: (A) A radius is half the length of a diameter; (B) A radius is not half the length of a diameter.

    15. Relation of Ideas or Matter of Fact?

    16. Analysis of the Fork: Problem 1 Is the Fork self-refuting? Hume’s fork is: all knowable propositions are either relations of ideas or matters of fact. But into which of these two groups does Hume’s fork itself fall? Is it knowable because of the relation of its ideas? It is certainly not an obviously analytic truth, like ‘2 + 2 = 4’. Is it true as a matter of fact? But what observations would verify or falsify it? Again it seems very difficult to know how to answer this. If I said, “There is a table in the next room”, we can easily think of observations that would verify or falsify such a statement, but what ones would verify or falsify Hume’s fork? It is because of these difficulties that some argue that the Fork is self-refuting, i.e. it does not fit into either of its own two categories.

    17. Problem 1: Is the Fork Self-Refuting? But, if we study 4.1-2 carefully we can see that Hume says that something is either a relation of ideas or it is not. This makes it seem as though the Fork is virtually a relation of ideas – it is a very obvious truth along the lines of ‘Either something is an animal or it is not’, or ‘Either something is a circle or it is not.’ But, Hume’s further explanation of the Fork is not something that is obvious by mere thought: if something is discoverable by mere thought then it tells us nothing about the universe. It certainly seems to imply no contradiction to say that something can be discoverable by mere thought AND that this something tells us something about the universe. Thus the Fork is not a relation of ideas but, in that case, it is hard to see what evidence could verify it as a matter of fact. Thus the Fork is self-refuting: it claims to be an item of knowledge and yet it is neither a relation of ideas nor a matter of fact.

    18. Problem 2: Crossovers Some people claim to have found examples of relations of ideas that do tell us something about the universe. The most obvious example is “I exist” or Descartes’ cogito ergo sum. Both of these are intuitively obvious and they tell us something about the universe. Perhaps Hume could dismiss these examples as highly unusual and so ‘singular’ that there is no need to alter his maxim that relations of idea are generally of no use when it comes to finding out what is in the universe.

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