Moore's reply to the sceptic

27 Setembro 2024, 13:30 • David Yates

Here we covered Moore's "refutation of scepticism". Slides available on Moodle. Main points covered:

Scepticism

25 Setembro 2024, 13:30 • David Yates

Summary

Cartesian Scepticism and its dependence on: (i) a sceptical scenario, (ii) a theory of knowledge as requiring certainty (elimination of all doubt), and (iii) a closure principle.

Desartes’ closure principle:

·        If I am certain that I am in this classroom, giving this lecture, then I can be certain that I am not dreaming / being deceived by an evil demon

·        Schematically: if S is certain that p, and p logically entails q, then S can be certain that q

Descartes’ modus tollens:

1.        If I cannot be certain that I am not dreaming / deceived by an evil demon, then I cannot be certain that I am in this classroom, giving this lecture

2.        I cannot be certain that I am not dreaming…

3.        Therefore, I cannot be certain I am in this classroom…

The sceptical scenario

Dreaming scenario: you could be having a lucid dream right now, in fact your entire life up to now could have been such a dream

Demon case: defined in terms of ability to deceive me about any proposition, can even suppose that all experiences and beliefs are false and implanted by the demon

·        These are sometimes taken to be thought experiments but I don’t think so!

·        Scenarios are defined in terms of phenomenological indistinguishability, so they cannot lend support to the claim that SH indistinguishable from actuality

Descartes epistemology: If I cannot be certain that I am giving this lecture, then there is a residual doubt over its truth and I cannot be said to know it

·        But is certainty really necessary for knowledge? What is certainty—is it a measure of subjective state of mind? If so, is certain belief sufficient for knowledge?

·        Moder epistemology rejects Cartesian claims about certainty—knowing does not require the elimination of all possible doubt!

Which closure principle?

C1: If S knows that p, and p logically entails q, then S knows that q

·        C1 clearly false—S may not know that p logically entails q!

C2: If S knows that p, and S knows that p logically entails q, then S knows that q

·        Something like C2 is needed if we focus on knowledge, but is it true? What if S fails to think about what they know and hence fails to draw the conclusion?

Easier to focus on justification (reason)

C3: if S is justified in believing that p, and S knows that p logically entails q, then S is justified in believing that q

·        We don’t need to worry about whether S has thought about it, since we can be justified in believing something even if we don’t actually believe it (contrast with knowing)

Justification as a necessary condition for knowledge

·        Mere true belief not sufficient (Plato, Theaetetus)

·        Justified true belief is more plausible as knowledge—at the very least, justification seems to be necessary for knowledge, so if you don’t have it, you don’t know

General form of closure arguments for scepticism

Depend on a sceptical hypothesis SH: you are in a version of the Matrix with no possible evidence that you are in it; you are a BIV; you are being deceived by an evil demon; etc.

Core component of SH (by definition) everything would seem exactly the same to you if you were in SH. No phenomenal, detectable difference between SH and real world.

1.        If you are justified in believing that you have two hands, then you are justified in believing that you are not in SH (instance of C3: “David has two hands” logically entails “David is not in SH” and David knows this)

2.        You can never be justified in believing you are not in SH

3.        Therefore, you can never be justified in believing that you have hands

Moore (from “Certainty”):

“I agree, therefore, with that part of this argument which asserts that if I don't know now that I'm not dreaming, it follows that I don't know that I am standing up, even if I both actually am and think that I am. But this first part of the argument is a consideration which cuts both ways. For, if it is true, it follows that it is also true that if I do know that I am standing up, then I do know that I am not dreaming. I can therefore just as well argue: since I do know that I'm standing up, it follows that I do know that I'm not dreaming; as my opponent can argue: since you don't know that you're not dreaming, it follows that you don't know that you're standing up. The one argument is just as good as the other, unless my opponent can give better reasons for asserting that I don't know that I'm not dreaming, than I can give for asserting that I do know that I am standing up.” (p. 32)

·        Problem for Moore: only focuses on dreaming

Matrix scepticism? Not quite right! Neo and others can find evidence that they are in the Matrix. Situation is very different for a BIV, whose total evidence is supposed to be the same as yours.

Modern version: BIV scepticism—support from cognitive science, idea of the brain as constructing perceptual models based on electrical input from sense organs (the BIV has by hypothesis all the same sensory inputs, so its experiences should seem to be the same)

Homework discussion / Introduction to logical fallacies

20 Setembro 2024, 13:30 • David Yates

On Friday we will continue to consider the differences between good and bad arguments, by considering what arguments are supposed to do and hence the various ways in which an argument can go wrong. Is soundness enough, or is there more to a good argument than that? Through our discussion of soudness, validity, and good argumentation, we will introduce a very important distinction that occurs a lot in contemporary philosophy: the distinction between necessary and sufficient conditions. As we will see, soundness is only a necessary condition - and is not a sufficient condition - for being a good argument.

Role of context in the fallacy of begging the question: the fallacy depends on whether we could come to know the premises independently of already knowing the conclusion. This means that our epistemic context - what we can and cannot come to know depends on context - is relevant to the fallacy of begging the question!

We will introuce some of the main fallacies of argumentation, including:

• "ad hominem" arguments (ataque pessoal)
• Begging the question (petição de princípio)
• The fallacy of "post hoc, erco propter hoc" (depois disso, por causa disso)
• The "slippery slope" (derrapagem, ou "bola de neve")
• The "strawman" fallacy (falácia do espantalho)
• The fallacy of composition (falácia de composição - vê também divisão)
• The fallacy of equivocation (equívoco - uma falácia de ambiguidade)
• The faulty analogy (a falsa analogia)
• The false dilemma (o falso dilema)

Vejam aqui uma guia das falácias em português: https://criticanarede.com/falacias.html

Focusing on fallacies will help us tell the difference between good and bad argumentation. As we will see, almost all arguments in public discourse are fallacious in one or (typically) more ways!

Reading

Before the Friday class, make sure you read Jim Pryor, "Guidelines on Reading Philosophy" (in particular the section titled "What is an argument?") , which is in the readings folder. We will discuss this in class, as it will help you when reading philosophy if you keep in mind what it is you should be looking for. It has to do, of course, with identifying the main conclusion and the arguments offered; and then assessing whether the arguments are any good...

Introduction to argumentation

18 Setembro 2024, 13:30 • David Yates

This week we will first introduce the course and the topics to be covered, and make sure that all students understand the attendance requirements and assessment methods to be used. We will then introduce the concept of a philosophical argument and the related concepts of validity and soundness.

• What is an argument?
• What is an argument for?
• What are (i) soundness, (ii) validity? Why are they important?
  

Summary of class 1

Examples of valid, invalid, sound and unsound arguments

Argument 1—sound

David is a man

All men are mortal

Therefore, David is mortal

Argument 2—valid but unsound (all propositions false)

David is a reptile

All reptiles can fly

Therefore, David can fly

Argument 3—valid but unsound (1 false premise, true conclusion)

If David is an ostrich (avestruz), then David walks on two legs

David is an ostrich

Therefore, David walks on two legs

Argument 4—invalid and unsound (but has true conclusion and true premises)

David is bald

Bald men have shiny heads

Therefore, David is a philosopher

Argument 5—???

Everything in this classroom is less than 60 years old

Vinicius is in this classroom

Therefore, Vinicius is less than 60 years old

Homework challenge: what is the difference between arguments 1 and 5? In class argument (5) started with “everyone in this classroom is less than 50 years old”. Some of you quite correctly pointed out that it is not obvious that Vinicius is in the scope of “everyone”—for that we would need an additional premise that Vinicius is a person, which would give the argument a different logical form to argument (1). To avoid that, we can change it to:

Every student in FLUL is less than 100 years old

Vinícius is a student in FLUL

Therefore, Vinícius is less than 100 years old

So: what is the difference between arguments (1) and (5)? Are they both equally useful? Could you use both of them to convince someone of their conclusions? Think about what you would need to do in order to justify the first premise in each argument. We will use this example next time to illustrate the role of context in one of the main logical fallacies.

Do arguments help us make progress? Isn’t the conclusion obvious if you accept premises?

Examples of arguments whose conclusions are not obvious:

Maths (Fermat’s last theorem—proof is 129 pages long, but deductively valid)

Knowledge argument vs. causal argument—both prima facie (this means “on the face of it”, or “aparentemente”) persuasive deductive arguments, but they have contradictory conclusions, neither of which is either obviously true or obviously false. These summaries are very rough indeed, for illustration only!

Knowledge argument aims to show that that states of consciousness cannot be physical: we could know the complete physical state of an organism without knowing what states of consciousness it had, or even if it had any at all. Hence, states of consciousness cannot be physical, and can be known only “from the inside”.

Causal argument aims to show that states of consciousness must be physical: states of consciousness cause physical behaviours (e.g. bodily motions, speech) but all physical events have sufficient physical causes. Therefore, states of consciousness must be whatever brain states cause these behaviours.

These arguments cannot both be sound. But which, if any, do you think is sound, and why? One of the primary tasks of philosophy is evaluating competing arguments such as these to see which (is either) is stronger. Of course you might think that neither argument is any good! That would not commit you denying both conclusions, of course: it would commit you to not having a view about either conclusion, at least not on the basis of these arguments!