Week 2: Reasoning & Philosophy of Science Flashcards
Reasoning
our conscious ability to make sense of the world around us to modify our understanding of the world around us by evaluating and using facts
Humans and animals do this all the time
Science history
historically knowledge was derived from authority, you have been a sponge, and the idea of systematically testing “truths” is often attributed to Galileo in the 17th century (though it was probably more common) e.g; Aristotle, Galileo and falling masses
Galileo’s Leaning Tower of Pisa experiment
a thought experiment in order to prove that all objects fall at the same rate, whatever their mass.
What are the 3 assumptions we can make about facts?
- Careful observation will lead the observer to collect an accurate fact
- Facts are independent of any theory (they lead to theory)
- Facts are firm and reliable (repeatability)
1 Careful observation will lead the observer to collect an accurate fact - how can this be influenced?
natural tendency to use our experience to make sense of what we observe. We see what our previous experience tell us/expects us to see. There is nothing wrong with this - this has guided some of the greatest scientific discoveries. You see what previous experiences tells you to see.
Search image
two observers do not necessarily see the same thing, search image is getting good at seeing something:
X-ray interpretation: Doctors practice looking at X-ray and to be able, to interoperate what others cannot.
Fish Eye colour: Dr Clare practiced looking at the fish eye colour until her ‘search image’ was able to identify eye colour because she got good at looking for something.
Observers accounts in criminology, medicine, and in the legal profession are notoriously bad.
2 Facts are independent of any theory
stair-case example, optical illusion doesn’t work on someone who has never seen stairs, they will only see lines on a page.
Having a concept of what stairs look like guides your ability to see and interpret the illusion.
3 Facts are firm and reliable
Facts change, our judgement about the validity of an observation is guided by what we know or assume. This makes facts just as fallible as our assumptions.
Scientific knowledge is based on facts established by observations. What is the role of experiments?
The art of an experiment is continual refinement. to improve the conditions or design/technology and see if the results are consistent.
Attempt to create objective observations rather than subjective ones, minimizing subjective observation and maximizing amount of independence from what you observe.
Reasoning is the way we make sense of facts.
What are the the most common forms of reasoning?
Inductive and deductive
Logic is very different to reasoning, although science is based around logic. What is logic?
When we use logic in common everyday ‘speak’ we are using it inappropriately. Logic is a set of rules, if something is logical it does not make it true. Logic is the basis of how we study “reasoning” but also math, economics, computer science etc.
Logic is not right or wrong, it is just a set of rule - nothing to do with correctness
Logical arguments:
- Philosophy is dull
- This lecture is on philosophy
Thus: - This lecture is dull
Is this logical?
Yes, but it does not make it true.
- A bird is a mammal This is also logical
- A crow is a bird
Thus:
3. A crow is a mammal
Is this a logical argument? is it correct?
This is logical, however it is not correct because premise 1 is incorrect.
We have drawn a false, but logical conclusion
Monty Python example:
All witches burn
All things that burn are made of wood.
Therefore, all witches are made of wood
All things made of wood have the same weight
All things that float have the same weight, all wood floats, a
All ducks float
Therefore if she weights the same as a duck she’s made of wood
Entirely logical argument, they have constructed logical argument yet it is false
What is inductive reasoning?
Build up a series of observations, which support a particular fact.
It is possible the fact is still wrong, we use probability to measure uncertainty.
All life forms are composed of carbon, hydrogen, oxygen, nitrogen, sulphur and phosphate.
All life has phosphate based DNA
This is alive
Therefore it is probable that it has phosphate based DNA.
Is this inductive? What is the probability that the next life form follows this rule?
This is inductive reasoning.
It is possible to find something that does not follow the rules - but highly improbable.
1.6 million species have been named, every-single one of them are phosphate based,
Probability of not being phosphate based in 1.6 million: 1
The Arsenic story
Phosphate and Aresenic have similar properties: atomic radius, electronegativity…
Biological form of P is PO33- which is similar to AsO43- if it gets into your blood will kill you
Mono Lake, eastern CA – Alkaline, this is a toxic soup of salt, with high concentration of arsenic.
Bacteria GFAJ-1, bacteria that lives in this lake, scientist found this and found that it could live off an arsenic base rather than phosphate. They argued that the case of life’s composition is proven false.
Is science mostly inductive or deductive?
Most science is inductive because we use a finite amount of available evidence to generalize about how all cases will respond.
Induction can never really demonstrate something completely.
How do we make good inductive conclusion?
*Make a large number of observations:
This can get ridiculous, should I burn my hand 100 times to demonstrate that fire burns?
True under a wide variety of conditions –
This can also get ridiculous; should I do it with different coloured socks?
- No contradictory cases – is this fair? There are very few rules that do not have exceptions
What are the problems with inductive reasoning?
- Humans see patterns: we have a perception of the world
* Humans are biased: we seek evidence to confirm our hypotheses.
Is inductive reason logical?
No, even if it may be correct your conclusion is based on observations
Observation ===|> Conclusion (NOT logical)
Copper example:
- Copper expands when heated
- Iron expands when heated It is however correct
- Gold expands when heated
thus
- All metals expand when heated.
This is not a logically valid argument
It is correct - but it is also possible to find a metal that does not expand
Animals can do inductive reasoning as well example, give example:
Two Monkeys Paid Unequally’
Monkeys understand that grape is unfair relative to cucumber, monkey able to reason inductively
What is the opposite of inductive reasoning?
Deductive reasoning
What is deductive reasoning?
You proceed from a general statement to a specific conclusion, this conclusion must be true given the previous statements – it uses logic! It is based on the principle of logic.