intuition and deduction thesis

what is a synthetic a priori truth?

• rationalists say some of the propositions we know are these

• synthetic: they make substantive claims depending on how the world is

• a priori: our knowledge of them is independent of experience

what is the overarching question in this unit

are there synthetic a priori truths? empiricists say yes, rationalists say no

what are some propositions believed by rationalists to be synthetic a priori truths?

• 7+5=12

• there is a prime number greater than 2

• I exist

• there is an external world

how do rationalists believe synthetic a priori truths can be grasped?

intuition and deduction

thesis claims that there are two ways genuine knowledge can be justified: by intuition, by deduction, or by both

what is an intuition?

an intellectual capacity to grasp the truth of a self-evident proposition directly and non-inferrentially

what is descartes’ name for a rational intuition and how does he rely on them?

clear and distinct idea

relies on them for some of his proofs and, using the intuition and deduction thesis he tries to derive certain synthetic a priori truths

we can apply deductive reasoning to truths we have acquired by rational intuition in order to gain other knowledge

can use this term interchangeably with intuition

explain clear and distinct ideas ie. diff between a sensory perception and this, and how to concieve of it

• while a sensory perception can be false, clear and distinct ideas are necessarily true

• the propositions expressed by them are indubitable

• something can be conceived of clearly and distinctly if it can be conceived to exist independently of anything else, or if it is possible for God to bring it to existence without bringing anything else into existence

• these clear and distinct ideas have been implanted into our minds by God and they contain eternal truths about the essence of things - eg. mind and matter

What is deduction

• some a priori knowledge can be justified by deduction

• inferential justification whereby the knowledge claim is a conclusion that has been derived from and follows necessarily from the premises ie. a conclusion that MUST logically be true

simplified version of descartes using intuition and deduction thesis and clear and distinct ideas:

• we can apply deductive reasoning to truths we have acquired by rational intuition in order to gain other knowledge

• eg. i might by intuition see that 3 is a prime number

• and that it is greater than two

• i might then by deduction conclude that thee is a prime number greater than two

• a priori knowledge has therefore been gained from intuition and deduction

overview of Descartes’ argument - are they intuitions or deductions?

1. cogito: a priori intuition

2. trademark argument: a priori deduction

3. cosmological argument: a priori deduction

4. ontological argument: a priori deduction

5. proof of the external world: a priori deduction

6. proof that the mind and body are distinct: a priori deduction

explain the cogito and why it is an intuition

• context: infallibilism to the point where nothing is knowledge unless it is indubitable bc of evil demon

• a priori intuition

• Descartes claims he cannot doubt that he exists though

• this is because by doubting he exists he is doubting he is thinking, which in itself is a kind of thinking

• if he is thinking there must be a thinker doing the thinking

• therefore he knows he is at least a thinking thing

• ‘i think therefore I am’

• this is knowledge gained through intuition because it is the non-inferential awareness of a truth because it has been discovered by thinking alone -ie. without any inductive or deductive reasoning

• not a deduction (despite the misleading ‘therefore’) because as soon as he starts thinking, it is self evident that he exists

explain the trademark argument and how it is a deduction

• the concept of god is like a trademark according to D, that god has stamped on our minds

• argument relies on the idea that a cause must have as much reality as the effect

1. I have the concept of god

2. i am finite but god is infinite

3. therefore god has more reality than my own mind

4. the cause of the concept of god must have as much reality as what it is a concept of (causal adequacy principle - this is an intuition)

5. therefore, while my mind can create concepts, it cannot create the concept of god

6. the only possible cause of the concept of god is god himself

7. therefore god exists

   • a priori because knowledge of it comes independently of experience and deductive because the conclusion that god exists derives from and follows necessarily from the a priori premise that the only possible cause of the concpet of god is god himself

Explain Descartes cosmological argument for the existence of god

• choose this or ontological in an essay don’t do both

• a priori deduction - there are arguments against this being the case tho

• cosmological arguments engage with the question of why anything exists

• i am not the cause of my existence because if i were i would have given myself all the perfections, but I do not have all the perfections

• something else must be the cause of my existence because something must be causing my existence over time and i do not have the power to do that

• what causes my existence must be a thinking thing containing the idea of god, because I am a thinking thing with the idea of god, and because a cause must have as much reality as its effect

• the cause which is the cause of my existence must also be the cause of its own existence because if it were caused by some third thing, then there would be an infinite regress of causes

• what also causes its own existence (and also my existence) is God

• therefore, god exists

explain descartes’ ontological argument

• a priori deduction

• through rational intuition of a clear and distinct idea of something we discover truths about that thing

• descartes states he has a clear and distinct idea of God and that that

• by exercising rational intuition the truth is revealed to him that god exists

• it would be as contradictory to say that god does not exist (when we have properly understood that he exists through rational intuition) as saying that the angles of a triangle do not add up to 180 (as understood through rational intuition)

• our reason for thinking existence belongs to god’s nature is that existence is a perfection and he knows by intuition that no supremely perfect being like god can lack a perfection such as existence

• therefore god exists

• a priori deduction because conclusion that god exists follows necessarily from the premises that existence is a perfection and god is perfect

descartes’ proof of the external world (part 1)

• a priori deduction

• we cannot know that physical objects are the cause of our perceptions (though we know from perception that we have perceptual experiences) because of the three waves of doubt

• there are two parts to this argument: an analysis of the idea of a physical object 2. a proof that physical objects exist

analysis of the idea of a physical object:

• when you melt a piece of wa, its sensory qualities change but you still think it is the same piece of wax

• you therefore understand a physical object to be what it is (extendable and changeable) on the basis of your mind alone and not on the basis of sense perception

• because if you were to merely trust your senses you would not have any reason to believe that the solid and melted wax were the same object as your senses would suggest that they are different

• that a physical object is extendable and changeable is a clear and distinct idea

descartes proof of the external world 2

the proof:

1. i have involuntary perceptions of physical objects

2. they cannot be caused by my own mind otherwise they would be voluntary - questionable

3. they must then be caused by something outside of me - god or physical object

4. they cannot be caused by god because that would mean that my belief that physical objects would be false, which is impossible as it would mean that god has decieved me

5. therefore the cause of my perceptual experience of physical objects is existent physical objects

6. therefore an external world of physical objects exists

descartes’ proof that the mind and body are distinct

• a priori deduction

• look at mind notes for this

hume’s fork as a response to the intuition and deduction thesis

• this disagreement is with the rationalist claim that some synthetic propositions are known a priori

• hume’s fork divides knowledge into 1. relations of ideas that can be discovered by pure thinking and 2. matters of fact that can be discovered by experience and memory.

• this implies that 1. all synthetic knowledge is gained a posteriori (matters of fact) 2. all analytic propositions are known a priori (relations of ideas)

• matters of fact: relate to what exist in the world. synthetic proposition. gained by observation or inductive reasoning - does not necessarily follow from premises. some of this is gained by causal inference if it goes beyond my experiences

• relations of ideas: tell us nothing about the world and instead concern concepts. discovered purely by thinking. product of deductive reasoning - ie. conclusion necessarily follows. asserting the premises and denying the conclusion then you contradict yourself

• threatens i+d thesis because it asserts that their central claim that some synthetic truths are known a priori is untrue - does not fit into hume’s fork

what is another issue with intuition (there may be no thing as non-inferrentially justified knowledge)

• could be argued that there is no such thing as non-inferrentialy justified knowledge

• that is, all knowledge has a justification in some other knowledge, and there is no knowledge which is self justifying in some sense

• opposes foundationalism: Rationalism in the form of the Intuition/Deduction thesis is also committed to epistemic foundationalism, the view that we know some truths without basing our belief in them on any others and that we then use this foundational knowledge to know more truths.

• there is no hierarchy of beliefs where some beliefs are more secure than others

• rather, beliefs in a coherent set are mutually supporting and no belief is in principle immune from revision

• goes against intuitions/clear and distinct ideas

argument against the cogito - challenging that there must be a thinking thing

Descartes’ response

• How does D know that there is an ‘I’, a thinking thing? his idea of this might have been implanted by the evil demon just as his sensory perecptions could have been

• even if there is thinking taking place, there might be thinking without an 'I’, something rather than the ‘I’ may be doing the thinking

• the most we can say is that there is a though - insufficient reason to think there is an enduring self

• hume: when we reflect on our inner life, all we see is a series of changing thoughts and feelings, not as unchanging ‘I’ ie. one and the same self persisting thoughts time which accompanies all the thoughts and feelings (think - is life permanent or perpetually in flux)

• D’s response: Thinking is a property of the mind, the mind is the ‘I’ or the enduring self. there could be no thinking without the mind just as there could be no ‘shiny’ without a shiny object

argument against the cogito - circular

descartes’ response

my evaluation

• ‘I exist’ that the argument is supposed to show presupposes the existence of the ‘I think’ premise - cogito is circular

• Descartes: but this criticism assumes the cogito is inferential, which it is not. Descartes is not saying that from the premise ‘i think’ he reasons ‘i exist’. rather, he is saying that ‘i think’ can immediately be seen to be equivalent to ‘I exists’ - ie. it is an intuition. it is self evident as soon as we are thinking we can know we are existing

• evaluation: criticism misunderstand the cogito and frames the conclusion as something inferred by the premises which it is not

Locke’s argument against the cogito

• includes reflections on the operations of our mind under the category of experience

• so not a priori and a rational intuition and instead a matter of experience

empiricist responses to the trademark argument - questioning causal adequacy principle; and Hume on concept of god and on causation

my evaluation

• why must the cause of the concept of x have as much reality as x?

• assuming we can make sense of the causal adequacy principle, we can still challenge whether the trademark argument is a rational intuition…

• descartes argument states that the human mind is unable to create the concept of god but hume disagrees. hume attributes the concept of god to humans infinitising in our own minds a set of finite properties we attribute to ourselves - goodness, power knowledge. super convincing because the idea that we can come up with the concept of god on our own challenges the premise of the argument so the argument falls - no longer a clear and distinct idea

• the truth about whether one thing causes another depends on experience. a priori reason alone will not prove that x causes y. whether or not it is true that ‘the cause of the concept of god must have as much reality as what the concept is of’, Descartes could only use causation to argue that god exists if he drew on experience

empiricist responses to Descartes’ cosmological argument - questioning everything has a cause, and infinite regress of causes

• descartes assumes everything has a cause. but what grounds does he have to believe this? it is not derivable using rational intuition/deduction. you only know whether something has a cause on the basis of experience. since we cannot have experience of everything this grand claim is unwarranted. it is logically possible that descartes’ existence is uncaused

• premise that there cannot be an infinite regress of causes: why not? our inquiries about causation can in principle go on forever? for a humean this is matter is not an empirical one either way - they do not in practice go no forever simply because a finite causal explanation is all we need for our practical purposes

empiricist responses to Descartes’ ontological argument - hume’s fork, kant’s argument that existence is not a predicate

response

my evaluation

• hume’s fork outlines that claims about what exists are matters of fact -ie. synthetic propositions. no existential claim, including the claim that god exists is analytic. otherwise the claim ‘god does not exist’ would be a contradiction, which it is not. that means that nothing exists necessarily. moreover, an existential claim is a claim about the world which depends on experience

• response: Whether it is right to say that ‘God exists’ is a claim about the world is questionable.  It is certainly not a claim about the spatial and temporal world, which raises the question of what ‘world’ means here. + god does not exist is a contradiction according to Descartes

• they need to agree on the basic terms here… disagreements on the key definitions: world, experience, knowledge. Hume’s account of knowledge and existence is more in line with ordinary usage ie. existential claims being about the world so is more convincing

empiricist responses to proof of the external world - russell

ignore for an essay

• that our perceptual experiences are caused by something is not a claim that can be justified using a priori reason alonse. like any claim about cause and effect, this claim is a posteriori

• Russell argued that the claim that physical objects exist is the best hypothesis based on inductive reasoning - best explanation. according to him, you cannot use deductive reasoning alone to support a claim such as physical objects exist or there is an external world. Because it is based on inductive reasoning, this hypothesis comes with a degree of uncertainty - so we cannot be certain that physical objects exist

• descartes’ argument depends on the existence of god and these arguments are lowkey dodgy