Theory of Knowledge TOK Lecture 7 Ways of

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Theory of Knowledge TOK Lecture 7: Ways of Knowing - Reason

Theory of Knowledge TOK Lecture 7: Ways of Knowing - Reason

Part 1: What is reasoning? And, how does it lead to knowledge?

Part 1: What is reasoning? And, how does it lead to knowledge?

What is reasoning? �A possible answer: reasoning is the mental processing of information. �But,

What is reasoning? �A possible answer: reasoning is the mental processing of information. �But, not all mental processing of information counts as reasoning. � The transformation of the electrical impulses sent down the optic nerve to the brain into a mental image is an example of mental processing of information. � But it is surely not an example of reasoning. �Does only the mental processing of propositional information (information that comes in the form of statements) counts as reasoning? �What about spatial reasoning?

What is an inference? �Drawing an inference involves deriving a conclusion from a premise

What is an inference? �Drawing an inference involves deriving a conclusion from a premise or set of premises. �Premise = a statement that supports/acts as a basis form/provides evidence for another statement. �Conclusion = a statement that is supported by one or more premises. �The process of drawing inferences is very important in understanding how reasoning can lead to knowledge – �i. e. , how reasoning can count as a “way of knowing”.

Two kinds of inference �Deductive inferences – when successful: if the premises are true,

Two kinds of inference �Deductive inferences – when successful: if the premises are true, then the conclusion has to be true. �Example 1: �(Premise 1) Steve is a bachelor. �(Conclusion) Steve is not married to Sally. �Example 2: �(Premise 1) All ravens are black �(Premise 2) X is a raven �(Conclusion) X is black

Two kinds of inference �Non-deductive inferences – Even when successful, the truth of the

Two kinds of inference �Non-deductive inferences – Even when successful, the truth of the premises makes the conclusion likely, but not certain. � Example 1: � (Premise 1) The window of my car is broken, and my laptop – which I left on the back seat – is missing. � (Premise 2) The best available explanation of this state of affairs is that someone has broken into my car and stolen my laptop. � (Conclusion) Someone has broken into my car and stolen my laptop. � Example 2: � (Premise 1) Most ravens are black. � (Premise 2) X is a raven. � (Conclusion) X is black.

Part 2: The relationship between reason and experience

Part 2: The relationship between reason and experience

Scientific Reasoning �Natural science is considered to be an area of knowledge in which

Scientific Reasoning �Natural science is considered to be an area of knowledge in which reason (a way of knowing) and experience (another way of knowing) come together. �But how does this work?

Inductive reasoning/inference � When philosophers first started thinking about scientific reasoning, they took the

Inductive reasoning/inference � When philosophers first started thinking about scientific reasoning, they took the process to be inductive. � What is inductive reasoning? � Reasoning from particular observations/experiences to general conclusions about the world. � Examples: � All tigers observed so far have been stripy. Therefore, all tigers are stripy. � The sun has always been observed to rise in the eastern sky. Therefore, the sun rises in the eastern sky every morning (including tomorrow morning). � The fallibility of induction � Inductive reasoning is a form of non-deductive reasoning. � The mere fact that all X’s so far observed have been Y does not make it certain the all X’s are Y: All swans observed by Europeans up until the 18 th century were white!

Inductive reasoning/inference � Hume’s problem of induction. � The sun has always risen in

Inductive reasoning/inference � Hume’s problem of induction. � The sun has always risen in the east in the morning. � Therefore, the sun will rise in the east tomorrow morning. � But, how do we know that inductive reasoning is reliable? � Surely we are not justified in making a particular inductive inference unless we are justified in believing that induction, more generally, is a reliable process of reasoning. � We know that induction is reliable because induction has always proved reliable in the past. � Uh oh, we are using inductive reasoning to justify the use of inductive reasoning! � This is like trying to find out if Bob is a reliable witness by asking Bob himself.

Hypothetico-Deductive Reasoning � What is it? � This is where you: � (1) Come

Hypothetico-Deductive Reasoning � What is it? � This is where you: � (1) Come up with a hypothesis/theory � (2) Work out what the empirical consequences of theory will be. � (3) Conduct experiments/observations and see if the results match those predicted by theory. � Example: � Einstein’s relativity theory entails – amongst other things - that nothing can travel faster than the speed of light. � If we fail to observe anything travelling faster than the speed of light – or doing anything else that contradicts theory – then theory stands. � If we do observe some event that theory says is impossible, theory falls.

Hypothetico-Deductive Reasoning �Advantages of the hypothetico-deductive approach: �Gets us around the problem of induction

Hypothetico-Deductive Reasoning �Advantages of the hypothetico-deductive approach: �Gets us around the problem of induction �We don’t need to assume that the future will be like the past. �If a theory makes a prediction and the prediction is not borne out, then theory is proven false, and that is that. �Disadvantages: �Only allows for falsification, never for absolute verification. �The fact that the predictions generated by a theory have come true so far does not mean that this will continue for ever. � E. g. – Scientists have not yet made a reliable observation of an object travelling faster than the speed of light, but such an observation might be made at some time in the future.

A priori reasoning: pure reason �A priori reasoning involves reasoning to conclusions in a

A priori reasoning: pure reason �A priori reasoning involves reasoning to conclusions in a way that does not involve any reliance on experience. �The example of mathematical reasoning: �Most mathematical reasoning involves the drawing of inferences from mathematical axioms or principles. �But how are the principles themselves supported/justified? �By experience? Surely not. �Because to understand them is to see that they simply must be true? � This answer actually seems more plausible.

Knowledge without reasoning? � Sometimes it looks as though we can gain knowledge is

Knowledge without reasoning? � Sometimes it looks as though we can gain knowledge is a way that doesn’t rely on other knowledge. � In fact, it seems like this must be the case: if all knowledge relies on other knowledge for support, then the chains of support will go on forever. � Self-evidence in logic and mathematics � Do you need a reason to accept that 1 + 1 = 2? � If you know what “ 1 + 1 = 2” means, then you know that it is true, right? � Basic empirical beliefs � What about beliefs about the contents of experience? � E. g. “I have a pain in my leg” or “I see something red”

Discussion questions for this week �What is reasoning, and how does it differ from

Discussion questions for this week �What is reasoning, and how does it differ from other kinds of mental processing of information? �What is an inference? �What is the difference between deductive and non-deductive inference? Can you come up with some examples of each? �What reasons do we have to prefer the hypothetic-deductive account of scientific reasoning to the inductive account? �Can there be reasoning without experience, or knowledge without reasoning?

Journal entry due week 1, Term 2, and reading. �What is the difference between

Journal entry due week 1, Term 2, and reading. �What is the difference between deductive and nondeductive inference? �Come up with two examples of each. �Reading for the start of term 2: �Nicholas Alchin, Theory of Knowledge, pp. 72 -91