The limits of knowledge

• Normal incredulity 


  Normal, everyday doubts about the world we live in. E.g a doubt about whether a mushroom 🍄 is safe to eat
• Philosophical doubt


  Beyond ordinary doubt, uncertainty over everything we know. E.g Are my hands real?
• Infinite regress


  A sequence of reasoning/justification, we can never come to an end with
• Normal incredulity only occurs where there is good reason to doubt a belief. E.g mushrooms

  • You see a mushroom in a field, is it edible?
  • It smells like an ordinary mushroom 🍄 In a shop
  • Deathcap mushrooms also smell like this however, what if it's a poisonous mushroom and not a field mushroom?
• Philosophical doubts are when you are doubting fundamental beliefs about who you are/what exists. E.g. are my hands real? Is everything around me real? 😭
• Theoretical doubt is when a philosopher doubts the truth of a proposition, a what if scenario. Making up and idea 💡 to explain something 😀
• Philosophical scepticism needs lots of proof to not be doubted, it may be impossible to remove doubt 🧐. It extends to doubting a whole set of beliefs, it has a theoretical rather than practical purpose.
• The infinite regress can be stopped by finding a belief that is true without evidence or supporting reasons, a foundation belief.
• Global sceptic 


  A view that questions the possibility of all knowledge. E.g existence of the external world
• Local sceptic 


  Questions the possibility of knowledge in a particular area of study. E.g. Is Utilitarianism the best way to make moral decisions?
• Local scepticism is the doubt 🤔 of a specific claim or area of knowledge.

  E.g

  • Doubting if we really know how many planets there are in the solar system.
  • Or doubting if an ethical claim such as Kantian ethics is really the best way to live.
• Global scepticism doubts all knowledge, doubting the existence of anything. For example, the brain 🧠 in a vat argument: what if we are not 🚫 walking, talking, human beings but just a brain in a vat controlled by a supercomputer 🖥️, directing everything, even our experiences. We cannot prove whether we really exist or if we are in fact just a brain in vat. 😄
• Reliabilism response to global scepticism: assuming we're not being deceived by and evil demon 👿/ brain 🧠 in a vat. Our perception would count as a reliable method of gaining knowledge because my perceptions could reliably cause me to form beliefs about the world.
• Reliabilists consider two scenarios:

  1. I am not 🚫 a brain in a vat: So, my perception is reliable as I'm living in the real world 🌍 and perceiving it accurately, my perception leads me to believe I have hands. My belief if true because I'm not a brain 🧠 in a vat. So, according to reliabilism I know I have hands
  2. "I am a brain in a vat". My perception isn't reliable, I'm a brain in a vat being fed artificial stimuli, my perception leads to the belief "I have hands". This belief is false, formed through an unreliable method. So, according to this situation you don't know if you have hands 😭
• The point of the reliabalism argument is that in scenario one, we can have knowledge of ordinary propositions such as : I have hands.

  Although we cannot know 😕 if we're in situation one or two and cannot be fully sure we know such propositions, we don't have to. We can know 😜 things without knowing that we know that thing.

  If we're not in a sceptical scenario, then knowledge is possible as knowledge is defined as a true belief formed by a reliable method and our perception is reliable if we're not being deceived so we can know basic propositions such as: I have hands ✋ 👌
• The limits of knowledge 😛 considers philosophical scepticism, whether it's possible to know anything at all!

  Descartes' 3rd wave of doubt 🤔 is an example of philosophical/global scepticism as it doubts whether we can trust anything we consider to be knowledge!

  Global/philosophical scepticism determines whether we can actually know anything 🤨
• • Ordinary doubt 🧐, or normal incredulity is doubting something in our everyday life
  • E.g. being unsure 🫤 when your friend's birthday 🎂 is
  • This doubt is practical and can be solved by using evidence 🧾
• • Philosophical doubt goes much beyond ordinary doubt and questions ❓ if we can know anything we think we know
  • For example, Descartes' evil demon 👿 doubt or the idea we might just be a brain 🧠 in a vat
• • The brain in the vat 🪣 example of philosophical doubt 🧐 is that what if all our "experience" is electrical signals which our brain 🧠 receives
  • We wouldn't be able to distinguish between being just a brain and being artfically fed "experience" and being in reality as we think we are!
  • For example, if you are a brain in a vat 🪣 you may think you're outside walking, but you're actually just a brain being given electrical signals that make you feel like you're walking - so you have the false 😓 belief "I am walking"
  • Everything we believe may be false and we have no way of knowing - we can question 😔 everything we think we know!
• • Local scepticism is the belief that nothing can be known within a certain domain
  • For example, someone may be a local sceptic about God, believing it's impossible 😭 know whether God exists 🙏
  • Local sceptics, however, still accept knowledge such as "I have hands" is possible
• • Global/philosophical scepticism is the view we can't know anything at all!
  • Global sceptic argue we can't know anything, even basic beliefs like 1+1=2
• • Descartes evil demon 👿 wave of doubt is an example of global scepticism
  • What if all our experience is just a deception from the evil 🙈 demon? And I can't be sure of any basic knowledge as the demon is deceiving me!
  • E.g. "I know 1+1=2" No you don't the demon 😈 is deceiving you and making your mind think the answer is 2 when it's actually 4!
  • The evil demon scenario is possible and we cannot tell otherwise, so, this undermines that we can justify our beliefs and doubts whether we can actually know anything we consider knowledge
  • Global sceptics argue all knowledge is impossible and we don't know anything!
• • Descartes responds to scepticism with several arguments
  • Firstly, he uses the Cogito to show that evil if the demon 👿 is deceiving him, Descartes can still be certain he exists
  • He also argues God exists using his trademark, cosmological and ontological arguments
  • And, since Descartes feels certain God exists he concluded he can trust his perceptions and existence of the external world as God is perfect and wouldn't deceive him
  • Descartes uses intuition and deduction to justify his perceptions, suggesting they are accurate, so he can trust his perceptions and ordinary knowledge 😛
• • However, there are many criticisms of Descartes' responses to scepticism from Hume
  • Hume's fork can be adapted so scepticism still remains!
  • Firstly, it's conceivable the evil demon could be deceiving Descartes into thinking "I exist" so the cogito is a matter of facts, not 🚫 known through intuition and deduction
  • It's also conceivable that the demon 😈 has deceived Descartes into believing in the causal adequacy principle, so he also cannot know God exists and the external world 🌎 exists A priori as they all believe in the causal adequacy principle
• Russell responds to scepticism and argues and external world existing that causes my perceptions is the best hypothesis:

  • P1: Either the external world 🌍 existing and causes my perceptions OR an evil demon 😈 exists and causes my perceptions
  • P2: neither situation can be definitely proven, so they must be treated as a hypothesis
  • P3:The first hypothesis explains my experience better than the second
  • C: Therefore, it makes the most sense to conclude a mind-independent external world exists and causes my perceptions
• • However, a global sceptic may respond to Russell's argument that an external world existing is the best hypothesis by saying sceptical arguments just show (e.g. a demon 😈) is possible, not that they actually existed
  • So, we still can't trust our knowledge
• • Russell may respond to the criticism that the demon arguement just shows it's possible we don't have knowledge by arguing this doesn't mean knowledge is impossible!
  • Just because we don't know 😭 for certain we're not being deceived, this doesn't mean we can't have knowledge
  • Russel could argue the infalliblism definition of knowledge Descartes' take is poor as certainty is not necessary for knowledge
  • Russel could argue ,yes, we might be being deceived by a demon and we can't know either way. But, if we assume we're not 🚫 being deceived (which is the best hypothesis) our ordinary justifications are still sufficient for knowledge
• • However, a sceptic could also doubt that the external world is even the best hypothesis - there's equal evidence 🧾 to support a global sceptic situation and that there is an external world 🌍
  • So, we cannot prove one hypothesis of another as both hypothesis are equal
  • However, it could be argued it still makes the most sense to assume an external world in order to allow us to live in the world 🌍 and trust our lives - it just rationally makes the most sense
• • Locke also responds to scepticism suggesting we have reason to justify our perceptions
  • Firstly, he argues our perception is involuntary (where's imagination isn't). We cannot choose what we see 🙈 or hear (e.g. we cannot help but feel the heat of the sun 🌞) suggesting perception is caused external to our minds
  • Locke also argued our different perceptions are coherent. For example, if I write ✍️ on paper, I can also read and hear the words and they will be the same suggesting a common reality which causes all our perceptions
• • However, Locke's responses to scepticism can be criticised
  • We can argue even if Locke can prove our perceptions are caused by an external force, it doesn't prove this accurately represents the external world
  • What if the external force causing his involuntary perceptions is a deceiving evil demon 😈, and not the external world
  • And, what if the demon 😈 is creating coherent experiences, making it seem like what is read on a piece of paper 📜 is the same as what was written - a demon would be capable of this
  • So, we still can't trust we're not 🚫 being deceived
• • Berkley responds to scepticism with his theory of perception: idealism
  • With idealism, "to be is to be perceived" so it's impossible for perceptions to be different from reality, because perceptions are reality
  • Berkley concludes his perceptions must be caused by God's mind a they are so complex.
  • Berkley argues reality is the perceptions God causes in us and God wouldn't be deceiving us because God's ideas 💡 are reality
• • Berkeley's response to scepticism can be criticised as idealism is arguably not 🚫 the correct explanation of perception
  • There are many issues with idealism; such as hallucinations, illusions, solipsism and the role of God
  • Particularly with hallucinations, If it's accepted hallucinations aren't real perceptions, what if all our perceptions are just hallucinations caused by an evil demon 👿?
  • So we can still doubt all ordinary knowledge as it may be caused by a demon