Reason as a source of knowledge

Analytic

A claim is analytic if the truth of the claim is contained in the meaning of the words in it.

So, if your understand the meaning of the words, you know whether the statement is true.

Whether it is true or false depends solely on the meaning of the words.

If a true statement is analytic then the negation (denial of) the statement will be self-contradictory

e.g. a triangle is a three sided shape

Tautology - where the same thing is said twice over different terms

Synthetic

A claim is synthetic if the truth of the claim is not contained in the meaning of the words.

You need to know more than the meaning of the words to know whether it is true.

Whether it is true or false depends on the way the world is.

e.g. my mother has red hair

Necessary

A proposition that must be true (or if false, it must be false), a state of affairs that must hold. A statement can be necessarily true or necessarily false.

e.g. a triangle has 3 sides

Contingent

A proposition that could be either true or false, a state of affairs that may or may not hold, depending on how the world actually is

A priori

Refers to the way in which we acquire and justify knowledge. Truths that can be known independently of experience, without the use of senses, are said to be known as a priori.

We can be certain of a priori knowledge prior to any experience.

Gained without any sense experience

You don’t need to go and find anything out from the world

It is acknowledged that we need experience in order to understand language and concepts, but the key point is that a priori knowledge is not generated on the basis of experience.

A posteriori

Truths that can only be known via the senses and so are dependent on experience are termed a posteriori.

Gained through sense experience

You need some kind of experience of the world to find out the answer

Truths can only be known via the senses (or inner feelings) and so are dependent on experience are termed a posteriori.

Empiricism

All synthetic knowledge is a posteriori. Apart from analytic knowledge (which tells us nothing new about the world), all our knowledge comes from sense experience. The view that all concepts are derived from sense experience. We are born with no ideas. As we have sense experiences, we form ideas in our mind. We can’t have an idea of something we’ve had no sense experience of.

Simple and complex concepts:

Simple impression (the sight of the colour brown) —causes→ simple idea (the idea of brown)

Simple impression (the colour brown) + the simple impression (the smell of tea) + simple expression (the taste of tea) —together-causes→ complex idea (the idea of tea) ←alternatively causes— complex impression (painting of a cup of tea)

According to empiricists like Locke or Hume, all concepts ultimately derive from sense experience, whether that is directly (for simple ideas) or indirectly (for complex ideas)

Hume’s copy principle:

For Hume, ideas are simply copies of our impression made by a rubber stamp or a printing press. We can replicate these copies in our mind and combine them to form complex ideas. Locke says that ideas come from sensation (sense experience) and also reflection. This could mean generalising across several specific ideas or noticing what is common to different ideas. (e.g. forming an idea of beauty by reflecting on your sensations of beautiful things).

Hume’s extreme form of empiricism

If you think you have a concept, but can’t trace it back to an impression, then it is not a concept at all. Although you may have a word for it, that word doesn’t actually mean anything.

Rationalism

We can have a priori synthetic knowledge by using our rationality/reason. Without sense experience, and just by thinking, we can figure out things we didn’t know before.

Innatism

We can have a priori synthetic knowledge because it exists within us innately. Since it’s already within us at birth, we don’t need experience of the world. Innatism is the claim that there is some innate knowledge, not derived from experience, but somehow part of the structure of the mind. Innatists claim that we can have synthetic a priori knowledge about the world, however, they may disagree with each other about which examples of knowledge are innate, but a key suggestion is knowledge of God. Innatists tend to claim that this kind of knowledge is

• there at birth

• a priori

• universal, meaning it is known by everyone

• clear and distinct which is self-evident, infallible and the foundation of all our knowledge.

Innate ideas

Knowledge or ideas that are in some way built into the structure of the mind, rather than gained from sense experience

Plato and universals

• Plato was puzzled by “the problem of universals” of the relationship between a concept and an individual instance of that concept.

• We seem to have a concept of beauty, but never witness beauty in its pure form, only imperfectly in different people and objects. So what is beauty itself?

• No real objects are perfectly circular. So our concept of a “circle” must not derive from our sense experience - it must be innate. This applied equally to all mathematical shapes

• Plato argues that numbers are universals and are therefore innate. Although you may have sense experience of various instances of two things (e.g. a pair of gloves), you never have sense experience of “two” itself.

• Another example from Plato is the concept of being equal. Because two things we can experience can never be exactly equal, we must not get our concept of equality from experience so it must be innate.

Plato’s argument for innate knowledge in standard form

P1. The slave boy has no prior knowledge of geometry/squares

P2. Socrates only asks questions; he does not teach the boy about squares

P3. By the end of the questioning, the slave boy is able to state an eternal truth about geometry/squares

P4. This eternal truth was not derived from the boy’s prior experience, nor from Socrates

C1. This eternal truth must have innately in the boy to begin with

Leibniz’s claim of sense experience

Sense experience only tells us about the particular thing we’ve experienced (an instance) - contingent truth. E.g. If we saw the sun rise this morning, we know that it rose this morning. We might think that it will rise every morning, but we can’t possibly have sense experience of it rising every morning. But, there seem to be some truths that we know will always be true (necessary truths). E.g. whatever our sense experience was, there couldn’t possibly be a time when 2 + 3 doesn’t = 5. “The senses never give us anything but instances, i.e. particular or singular truths. But however many instances confirm a general truth, they aren’t enough to establish its universal necessity; for it needn’t be the case that what has happened always will - let alone that it must - happen in the same way”

Plato’s Theory of Forms

• concept innatism = the claim that some of our concepts are innate, not derived from experience, but somehow part of the structure of the mind

• everything in the world is imperfect and changing. (e.g. Circles, universals)

• But we have the innate idea of perfect circles and universals. So they must exist somewhere else, not in the material things of this world.

• These perfect ideas (or forms) exist in The Realm of Forms, which is non-physical and eternal.

• Physical objects in this world are imperfect copies of the forms

• Our souls are the forms of us, which lived in the Realm of Forms before we were born, and will return there after we die.

Knowledge of the forms

• we have forgotten most of these “forms” but they are in us innately and Plato believed that through a process of reasoning, we can achieve a perfect understanding/apprehension once again.

• although this theory of forms is not widely supported today, Plato’s account contains some of the classic features of innatism that have been repeated through the ages

1. Innate ideas are “in” us, although we might not be aware of them (exactly like a forgotten memory is “in” us)

2. We can realise these innate ideas through a priori reason

3. Innate ideas provide timeless truths

Necessary truths

truths that have to be true - they couldn’t possibly be false. We’ve already looked at some examples such as “bachelors are unmarried”. Leibniz uses the laws of logic as examples of necessary truths, such as “it is impossible for the same thing to both be and not to be”. Everyone uses the sort of knowledge all the time, 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”. Leibniz argues that we come to know these innate truths by “attending to what is already in our minds”.

Leibniz’s law/the identity of indiscernibles

a metaphysical principle stating that if two entities are identical (numerically one and the same), they must share all the same properties.

Leibniz’s argument for innatism

P1. The senses only give us particular instances

P2. A collection of instances can never show the necessity of a truth

P3. We can grasp and prove many necessary truths

IC. (P1 + P2 + P3) Therefore the necessary truths that we grasp with out mind do not derive from the senses

MC. Therefore, our knowledge of necessary truths must be innate.

Leibniz’s marble analogy

Leibniz disagrees with Locke that the mind is a tabula rasa or “an empty page”. In contrast Leibniz says the mind is like a block of veined marble - the marble cannot be cut into any shape; the shape is in part dictated by the veins which are already there. It is the job of the sculptor to work with the veins to create the desired shape, they do not have a “blank slate” which could create any shape at all. They are “revealing” shapes which are already there. Leibniz argues the mind is like the veined marble in that it has pre-existing knowledge of necessary truths and logic which are “revealed” by sense experience or learning and which give shape to our knowledge. The ease with which we know these truths implies we already have the shape of them within us (as pre-dispositions and natural tendencies to knowledge rather than “actual thinking”), like a block of marble already containing the shape of Hercules would be more easily revealed.

Ockham’s razor

The principle that states we should not put forward a hypothesis that says many different things exist when a simpler explanation will do as well. “Do not multiply entities beyond necessity”. A simpler explanation is a better explanation, as long as it is just as successful.

The mind as tabula rasa

The idea that the mind can be compared to a tabula rasa (which is Latin for blank tablet or slate) goes back to the early days of Western philosophy, where we find it in the writings of Aristotle, but it was Locke who gave the theory its first clear articulation. The tabula rasa theory works as a powerful argument against the theory of innate ideas. For if it can be shown that our ideas come from experience, then claiming that we have innate ideas would seem to be an unnecessary theory and so it would be unreasonable to hold it. This argument implicitly relies on a principle known as Ockham’s razor, which is the idea that, wherever possible, we should always go for the simplest explanation. (The idea of the “razor” is that we should shave off any unnecessary elements to an explanation.) Locke uses the example of our ideas of colours to make the case, but it suggests that it will apply to any supposedly innate idea. He argues that it could be the case that:

a) we are born with an innate idea of each colour

And it certainly is the case that:

b) we see colours with our eyes.

The question is, why would God, or even nature, bother with a) given that b)? It is a simpler explanation to say that our idea of colour is derived from b). Claiming a) seems to add no extra explanatory value and so, according to Locke, is an “absurd” additional claim. The general principle in play here is that we should go for the simplest explanation - in other words, Ockham’s razor.

*Locke’s criticism 1: the theory of innate ideas is unnecessary

Locke uses Ockham’s razor to argue that if we can explain the existence of all our concepts without the need for supposing that innate ideas exist, then we should do. Innatism claims that some of our ideas cannot have come from sense experience alone e.g. knowledge of universals (P&L) and knowledge of necessary truths like laws of logic (L) - Locke attacks this saying we can equally explain these ideas, and without postulating the existence of more entities i.e. innate ideas, and additionally the further entities on which these rely, e.g. a realm of forms. Innatism argues there is not equal explanatory power without postulating the existence of innate knowledge - no number of individual sense experiences can lead to knowledge of a universal or necessary truth.

Locke’s criticism 2: No knowledge is universal

Many people in Locke’s day argued that certain ideas must be innate because they are universally accepted. Locke says that whichever idea the innatist suggests (such as simple mathematical concepts), although it may be the case that most people share the idea, there are no ideas that everyone shares. For instance, he claims that “children and idiots” do not have these ideas. So the argument that they are innate because they are universal, fails.

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?

In response, Leibniz points out that universality cannot be either a necessary or a sufficient condition for innateness. There could be ideas that everyone shares that are not innate, they all just happen to agree. And God could give innate ideas to certain people and not others. Leibniz is agreeing with Locke that universality is not a good argument for innateness. But he still thinks there are other good reasons for accepting innate ideas.

Locke’s criticism 3: the mind must be transparent

In response to Locke’s criticism of universality, some innatists have claimed that there are innate ideas which “children and idiots” have, they are just not aware of yet. The ideas are in their mind from birth, but they don’t know they are there.

Locke argues that this can’t be the case. The mind must be “transparent”, so that any ideas which are in it, we are aware of (this doesn’t mean we have to be thinking of them, but that we have thought of them at some point). Otherwise, Locke asks, in what way can they be said to be “in the mind”? He argues you cannot have something "in the mind" without ever having known it is there.

Leibniz responds by arguing that we can have innate ideas which we are unaware of. (He was way ahead of his time here in effectively suggesting the idea of “subconscious” thoughts.)

Locke’s criticism 4: reliance on the non-natural

Most innatists of Locke’s time claimed that innate ideas are put into our minds by God. As we saw above in his first criticism, Locke believes that these same ideas can be explained naturally, without the need for anything supernatural like God. 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.

A modern response to this is that there are forms of innatism that don’t rely on anything supernatural. Chomsky argues that our ability to rapidly learn language is only possible if we all have an innate idea of grammar. Others argue that we all have an innate sense of morality. Many people believe that through evolution, we have developed innate instincts to interpret and respond to the world in certain ways. This non-supernatural form of innatism is often called nativism.

Locke’s criticism 5: Self-evidence

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, 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).

“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.

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.

The empiricist can respond to Plato by claiming that our concepts of universals really are based on sense experience. For example, by experiencing lots of beautiful things, we can form the concept of the beauty by working out what these things have in common. And we have the concept of two by experiencing two things.

Although this may seem plausible for the case of small numbers like two, I can have the concept of the number 8,346,231 without ever having seen a collection of that many things!

Similarly, the empiricist may convince you that you have derived the concept of circle from your experiences of circular things. But Descartes responds to this by pointing out that he can form a concept of a thousand-sided shape, even though he has never experienced one, and he can’t even imagine one.

“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 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.

the mind as a “tabula rasa” - locke

the mind is like a blank slate. the sense organs allow us to have experiences. these experiences are imprinted in the mind as ideas. one result of the tabula rasa view is that individuals without working sense organs will be unable to form ideas associated with that sense organ

Empiricism criticism 1: Hume’s Fork

Hume’s fork is his distinction between two types of knowledge. Anything that can be known must sit on one of the two prongs: Relations of ideas (analytic propositions) and Matters of Fact (synthetic propositions). Anything which is neither can contain nothing but sophistry and illusion. Hume argues for empiricism that impressions are both necessary and sufficient for ideas, where you can’t have an idea without having had the sense impression and every time you have a sense impression, it generates an idea.

Empiricism criticism 2: Impressions are not necessary

Hume’s missing shade of blue example: Hume imagines a person who has seen every shade of blue except one - say a particular shade between two others on a colour gradient. If you showed them a blue colour gradient, they would be able to imagine the missing shade of blue in between two colours despite never having seen it. This contradicts his claim that every idea must be derived from a prior impression. The copy principle said every idea has a corresponding impression but there is no copy in the case of the missing shade of blue - no corresponding impression - just a lone idea. This undermines the claim that all ideas are just copies derived from experience.

Response (simple and complex ideas): We can form an idea of that particular shade by combining the idea of blue with the ideas of darkness or lightness. So our concept of the missing shade does derive from sense experience.

Problems with the response: If the idea of this shade is a complex one, isn’t every idea a complex one? Every example of blue is of a particular shade (dark-blue, turquiosey-blue, sky-blue, etc). So could we ever have a simple idea of blue? If we couldn’t have a simple idea of blue, then we couldn’t combine it with anything to form a complex idea of a particular shade

The empiricist can claim that we can’t in fact imagine the missing shade. Then they can stick with the copy principle.

Empiricism criticism 3: Impressions are not sufficient

Wittgenstein’s “tove” example:

• Sense impressions are not sufficient for ideas

• E.g. “Tove”: you have the sense impression, but this isn’t enough to give you the right concept.

  • If empiricism were true, then when we had the first sense experience of tove (the pencil), that should have automaticallky created in us the right idea

  • But even after the sense experience, we still don’t know what the idea is

  • “tove” could mean pencil. But it could also mean “thing made of wood” or “physical object” or “yellow” or “one” or “mine”.

  • Even if we had loads of sense experience (by looking more closely, sniffing the pencil, touching it, tasting it, etc.) that still wouldn’t tell us which part of sense experience is being referred to.

• You need someone to explain which aspect of the sense impression of the word is referring to.

• So, we need more than just the sense impression itself to give us the concept/idea

• Lots of other concepts seem to require a certain context/explanation on top of sense impressions.

• E.g. “justice”. Maybe there are sense impressions that are relevant, but you need other information in order to form the concept. And this other information isn’t in the form of sense impressions

• So, some concepts require something else in addition to sense impressions.

Leibniz’s argument: Innate principles: the argument from the necessity of truth

Leibniz is suggesting that the senses can only reveal individual instances and cannot confirm a general truth. Leibniz claims seeing individual instances is never enough to establish the necessity of a general truth. People might be tempted after seeing lots of instances of a phenomenon to claim that their senses have proven the phenomenon must happen in the future. All we can know is that in the past this is the way the universe might just drift away. All we can know is that in the past this is the way the universe has worked, but as Leibniz claims, it needn’t be the case that what has happened always will - let alone that it must - happen in the same way. Senses might provide a guide into the future, but they do not prove that any generalisation must be the case or will always apply. In contrasts, mathematical truths are cases where truths were necessary/universal and grasped by the mind, not the senses. He used a metaphor of a block of marble - one that has specific “veins” running through it. The block of marble does not contain the fully formed statue, but has the “inclination” or “tendency” to take a particular shape when struck. Likewise, we are not born with innate ideas fully formed, since we need the experience of the senses to gain ideas, but our minds are structured such that certain ideas and principles will appear once prompted by the senses ideas and truths are innate in us - as inclinations, dispositions, tendencies, or natural potentialities, and not as actual thinkings.

Leibniz’s argument: Innate principles: the argument from the necessity of truth in standard form

P1. The senses only give us particular instances

P2. A collection of instances can never show the necessity of a truth

P3. We can grasp and prove many necessary truths (such as mathematics)

C1. Therefore, the necessary truths that we grasp with our mind do not derive from the senses

C2. The mind is the source of these necessary truths

C3. These ideas are known innately

Hume’s copy principle

Hume’s empiricist epistemology distinguishes between two types of experience - impressions (the actual perceptions we have when we see, hear or touch things) and ideas (faint images of these impressions in our minds when thinking about or remembering or reasoning about these impressions). According to Hume, ideas can be traced back to some original sensory impression. They are copies that exist in the mind of these original impressions. This is known as the copy principle. Hume also distinguishes between simple and complex ideas. Simple ideas are the most basic components of thought and can’t be broken down any further - for example, the specific shade of blue you see in the sky. Complex ideas, in contrast, are combinations or arrangements of these simpler ones - like imagining a blue door, which combines the simpler ideas of “blue” and “door”. Hume’s point is that even our most complex thoughts can ultimately be broken down into simple ideas, and every simple idea can be traced back to a corresponding impression.

Deductive

Deductive arguments operate on the principle of logical necessity, aiming to provide conclusions that follow necessarily from the premises.

So rather than appealing to probability or likelihood, deductive reasoning concerns whether the structure of the argument guarantees the truth of the conclusion.

If premises are true, it is logically impossible for the conclusion to be false.

Inductive

Inductive arguments are those in which the premises make the conclusion probable rather than logically necessary.

They often involve drawing general conclusions from limited observations, but more broadly they aim to establish what is likely to be true given the evidence, rather than what must be true. So, while inductive arguments do not guarantee absolute certainty, they offer insights and probabilistic reasoning.

Despite not being logically watertight, they provide support for the conclusion

Intuition & Deduction Thesis

Rationalism: there is some synthetic a priori knowledge known as reason.Descartes proposes that we can gain synthetic a priori knowledge through reason alone, through two operations of the mind:

• Intuition: being able to understand something just by thinking about it - intuition is not a “gut feeling” or “instinct” but is an intellectual capacity to grasp the truth of a self-evident proposition directly and non-inferentially. (Descartes speaks of the “natural light of reason” and “clear and distinct ideas”)

• The second key operation of the mind is deduction, which Descartes describes as “The inference of something as following necessarily from some other propositions which are known with certainty”. Deduction: figuring out what must follow from certain claims - it is inferentially justified in virtue of being the conclusion of a deductively valid a priori argument (ie one all of whose premise are knowable a priori) - Descartes’ own words: “the inference of something as following necessarily from some other propositions which are known”.

The first indubitable truth - Descartes’ cogito

The cogito is Descartes’ claim that he exists: “I am, I exist”. In the cogito, Descartes here understands himself as a thinking thing that is clear and distinct (and is therefore not necessarily identical to his body). Even if an evil demon is deceiving him about the existence of physical objects and thereby knowledge of the external world/empirical knowledge/knowledge that is justified empirically/synthetic a posteriori knowledge - along with knowledge of mathematical truths (a priori knowledge) - the evil demon cannot deceive him about his own existence since, if the evil demon is deceiving him, he must exist to be deceived. It is a true belief that is indubitable/immune to doubt/certain and therefore counts as knowledge. It is an a priori intuition, meaning it is not known through sense experience/empirical observation and it is a direct or non-inferential awareness of a truth which has been discovered by thinking and reasoning alone. It is therefore a foundational piece of knowledge.

Descartes’ cogito as a deductive argument

The cogito could be presented as a deductive argument - something like this:

P1. I am thinking

P2. (hidden premise) All thinking things exist

C. Therefore, I exist

Descartes explicitly denies the cogito is a deduction, but rather “a simple intuition of his mind shows it to him as self-evident”. In the Mediations, Descartes needs the cogito to work as a simple intuition (rather than a longer argument) as he is still working under the assumption that a demon may be deceiving him, and this could affect the validity of his memory (which is required in a longer argument)

Descartes’ cogito as a transcendental argument

Transcendental arguments attempt to “transcend” doubt. They work by arguing that a certain feature (in this case existence) is a pre-condition for doubt to exist. If so, you cannot doubt you exist, as you need to exist in order to doubt. This seems a plausible approach, but again might be too complex to count as a single intuition, which Descartes may need to overcome the demon challenge.

Descartes’ cogito as a self-verifying thought

Descartes often emphasises the temporary, fleeting nature of the cogito; “I am, I exist, must be true whenever I assert it or think it”. This suggests that the truth of the cogito is revealed in the very act of performing it. The thought that “I do not exist” is self-defeating in its performance - it is an assertoric inconsistency. In this way the thought “I am, I exist” may be self-verifying because asserting the opposite is self-defeating.