Lecture 2 – The scientific revolution
1. The scientific revolution
• Background: the scientific revolution (1550-1700)
® Before 1550, people thought they’d pretty much found the answers to the
major questions about the world.
® There was no science going on before 1550 because people thought they
had found the answers to the major questions about the world: religious
answers. It depends on where you live in the world or what religion you
belong to.
® When you look at scientific disciplines, they had a detailed story which
was derived from a theological reasoning or from bible scholars who
thought the bible provided the most important clues to questions about
physics, chemistry, psychology and medicine.
® If you look at astrology, people back then thought that earth was in the
centre of the universe (god created earth as the summon of his creation
because that was the place where men was put). They thought that all these
heavenly bodies were able to move in the way they do because they were
attached to certain crystal spheres (they couldn’t just float). People thought
these spheres were perfectly sphere. The stars were attached to the most
outer sphere.
,® If you look at chemistry, the four basic elements which make up everything
that exists on earth and in the universe: fire, earth, water and air.
® If you look at medicine, they believed that there are four certain fluids: blood,
yellow bile, black bile and phlegm. If you are healthy you have the right
combination of those four elements but if you start to get ill, then one of the
four elements is starting to dominate the others. One of the most important
elements of medieval medicine was bloodletting; get rid of blood because it
had become to dominate in the body = become better.
,® If you look at psychology, they thought that the ways humours were collected
in the body depended on their characters.
® They had a complicated way of thinking about what the world was like, it was
not based on experimentation. They were not testing these theories for reasons
such as why question something that is god given and cutting in bodies is a
secretion of the holy human body (for example to test if the four humors are
actually present in a human’s body.)
• This picture of the world had changed completely 150 years later
® In the 16th and 17th century people started experimenting, scientists
started to discover new things about the world.
® In astronomy, Copernicus discovered that if you put the sun in the center
of the universe and you hypothesis that all the other heavenly bodies are
orbiting about the sun, than you get much better predications about what
will be visible at night. People tried to predict where Venus or Saturn will
be in a month, but all these predictions were wrong. Copernicus found that
if you reverse the center of the universe, if you put the sun in the middle
and hypotheses all the other planets are revolving around that, you get
better predictions.
® The sphere theory was also let go off because Newton came up with a new
theory about how the heavenly bodies were able to float. He hypothesized
that it was due to a force called gravity: attraction between any two bodies
in the universe (earth attracted by the sun). Every two objects in the
universe have a mutual attraction and that attraction becomes bigger the
heavier an object becomes = the sun is heavier compared to all the other
objects, so it’s all the other objects falling towards to sun and because its
falling in a certain speeds it starts to orbit in an elliptical sphere.
® In chemistry, scientists found that there are way more elements and that
earth, fire, water and air were not really elements. They had more technical
names such as hydrogen and oxygen.
® In medicine, people started to experiment. Late 16th century, men from
England discovered that blood was pumped around by the heart in the
body (function of the heart). Later they discovered that blood was a
transport system from oxygen and nutrients.
, • Result: clash between church and science (who used methods and new
insights)
® People started to doubt whether knowledge existed at all.
® This was also the era in which people started to question the catholic
version of Christianity. Protestantism was formed.
® Different worldviews were flowing around: the old rich powerful church,
the new Christians (protestants) and the scientist. They all had a different
picture about the world.
® Galileo: “and yet it moves” = the earth moves around the sun. Supported
Copernicus’s theory.
2. Due to this, there was a rise of skepticism = we do not have any knowledge.
a. A definition of knowledge
® They used an ancient definition of knowledge to justify this claim, because
if you claim as a philosopher that we don’t have any knowledge at all, you
need a definition of knowledge to begin with. There definition of
knowledge goes back to Plato.
® Plato tried to find a definition of knowledge that gives us both the
necessary and sufficient conditions for it.
® An important method for finding definitions: determine the necessary and
sufficient conditions.
® Necessary condition: if a does not have the property S, it is not X
® Sufficient condition: if a has property S, then it must be an X
® A good definition is a list of individually necessary conditions that is
jointly sufficient.
® What are the necessary and sufficient conditions for knowledge? Plato:
there are three conditions that are individually necessary and jointly
sufficient:
o Belief: you must believe X to know X
o Truth: X must be true
o Justification: your belief must be justified.
® There must be a reason to believe that X is true (it needs to be based on
something). Otherwise, it is accidently true.
b. Scepticism
The sceptics said, if this is the definition of knowledge (it must be believed, it
must be true, and it must be justified) = then we do not have any knowledge:
• … because: although we have beliefs…
• … and some of those could be accidentally true…
• … we can never be certain that they are true and hence we do not have any
justification. (skeptical argument)
, Montaigne said that if you think about the arguments that people use, they are
never really good. You can’t be certain that our beliefs are true and therefore
there is no justification that our beliefs are true. Most of his arguments were
skeptical arguments about the major source of justification used in daily life.
For example, to convince people that something is true, we use observation or
evidence that we can show someone. The sceptic said that observation is not
reliable in some cases (sensory information)
® He used the idea that if you put a stick in water, it looks broken, but it actually
is not broken. Our eyes are not always reliable. From that he drew the major
conclusion that if you sometimes can’t trust your eyes, and you don’t know
in which cases you can and cannot trust your eyes, you never have
justification to rely on observation.
® This counts for all optical illusions.
® The main message of perception is that there is always a layer of interpretation
going on. You also see the interpretation and never the actual thing in itself
(optical illusion) and this creates skeptical arguments.
® If in some cases you know your eyes are deceiving you, but you do not know
in which cases, then you never have justification to use observation as a
justification for your beliefs.
3. There are also two historically influential answers to those skeptics: people who did
believe that we have knowledge. These were people on the side of the scientists, they
were developing new theories about all sciences and they thought they did have a way
to acquire knowledge about the world.
The two most famous movements were rationalism and empiricism.
a. Rationalism
® Rationalism: we can be certain about certain things. There is a list of things
that we can be certain off.
® Example: Descartes did a thought experiment and said let me doubt
everything I believe (I can doubt my age, that I am sitting behind my desk,
but what I cannot doubt is at least that I exist, because I am doubting,
hence I must exist).
® The point is that Descartes was a rationalist and that rationalism involves
thinking that some believes are certain and true (mathematical beliefs).
® Rationalists think that if we can be certain about a few beliefs and we can
use a method to get from those few beliefs to more beliefs, that we can
maybe use that method to derive other knowledge about the world. We can
derive other knowledge from the world, from those few things we are
certain about.
® Sensory observation is unreliable = so we can only rely on clear and
distinct ideas = example: cogito argument (Descartes knows he is existing
because he is doubting).
® Descartes says if you have clear and distinct ideas then you can use
deduction to infer new knowledge from those few and clear ideas.
, ® Deduction = if you know the premises are true, you are absolutely
certain that the conclusion is also true.
® Rationalist theory = start with clear and distinct ideas that are certain to be
true then you use deduction to derive new knowledge from that.
® Deduction = certain knowledge. Knowledge as certain as the premises.
b. Empiricism
® Empiricism: sensory experience is the source of all knowledge.
® Some sensory experience is certain. Such as when you see an apple, you
might doubt whether it’s a real apple or not. However, you can’t doubt that
you see the color red or if you bite am apple you taste a sweet of sour taste.
You can break it into certain elements such as the round shape, the sweet
or sour taste, the color of the apple = these elements show that there is
certainty (empiricists argument).
® Tabula rasa theory is connected to this, which means that babies are born
without any knowledge and that given that we do have knowledge when
we are adults, everything has to be learned through sensory experience.
Either because we observe things as baby, kind or adult or because our
parents or teacher tell us. The idea is that because babies are born without
any knowledge all our knowledge has to come from sense experience at
some point.
® Bacon was an empiricist: there is nothing in our mind that was not first in
our senses.
® Empiricists believed that induction was the way to acquire knowledge.
® Induction = if you are certain that the premises are true, it becomes
more likely that the conclusion is true.
® Induction = fallible knowledge. Induction makes a probable conclusion on
the basis of the premises.
® Mode of reasoning/ empiricism theory = start with observation and you
use induction to derive knowledge from that. Collect as many observations
as possible, guided by theories, then you use induction to show that it is
probable that something is true.
,® Empiricism is the common sense approach (fits with everyday life of
acquiring knowledge such as using eyes and ears and it fits with our ideas
of how science works.
® Of course you will have to make observations before you can know how
the world works…
® Also seems to fit in with our ideas about science.
® However, there are two important problems for the empiricist:
1. Empiricism seems to be vulnerable to scepticism, although they do have
a response to the sceptics (such as seeing an apple as a round thing or
tasting an apple as an apple)
® For example, when looking objects with color. When light hits an object,
every object has certain properties to absorb certain types of wavelengths
of light whereas it reflects others. It’s a matter of fact that certain arrays
and wavelengths hit our retina and our brain interprets the light waves to
be a certain color (the object). We don’t know if that’s the actual color of
the object and if we all see the same color.
® So, the problem is that observation is unreliable
2. The problem of induction
® The sceptics ask: how do we know that induction is reliable? Maybe it
only works in some cases but not in others.
® Empiricists answer is that: it has worked well in the past (e.g.: my alarm
clock worked well this week so it will work well tomorrow).
® Problem: this answer itself presupposes that induction is reliable.
, ® You are only justified in believing that induction is reliable, when you
presuppose that induction is reliable!
Here you are using induction, to justify induction and that is a problem
according to the skeptic.
Another example is being instructed to write an essay but not being allowed to
use Wikipedia because it is not reliable. Suppose that a student shows the
teacher a source from Wikipedia that argues that Wikipedia is reliable and
asks if this is a good argument. The teacher will say no because she is already
doubting if Wikipedia is reliable, so it doesn’t help to show the teacher a
Wikipedia page about reliability. This also counts for the skeptics. The
skeptics are skeptical about induction, then you cannot use an inductive
argument to show that induction is reliable.
Summary:
• The scientific revolution (1550-1700) led to questions about knowledge
• What is knowledge?
® We can find a definition by looking at necessary and sufficient conditions
® Plato’s answer: You know about X when your belief about X is true and justified.
• Do we have knowledge?
® Scepticists say no: we do not have any knowledge
® Montaigne: both our senses and reason are unreliable.
• What is the source of our knowledge?
® Rationalism (response): Only clear and distinct ideas and deduction lead to certain
knowledge.
® Empiricism (response): sense experience is the source of all knowledge
® Empiricism seems more sensible but there are two problems: (a) scepticism, (b)
problem of induction
Lecture 3 - Confirmationism
• Part 1: Is science just an opinion (and if not, why not)?
® Lecture 03: No, because science is based on empirical evidence.
,In the 20th century a new type of empiricism developed that argues that the thing that makes
science unique is completely tied to empirical evidence. We can derive the structure of
scientific theory from our primary sensory observations
® What happened was the: Annus Mirabilis in 1905 (the year of miracles). This was
the year in which Einstein within a few months time had revolutionary ideas on a
number of different scientific domains (physics and astronomy).
® Einstein proved four things that was a revolution in the history of science. E.g. he
proved Newton wrong.
® March 1905: Light consists of particles, not waves.
® May 1905: Mathematical proof that it is very likely that atoms exist.
® June 1905: Relativity theory. Einstein accepted classical relativity: e.g. when you
walk in a plane to the bathroom you feel like you are walking 5km/h but someone
looking from land who sees you walking to the bathroom will see you walking
695km/h (take into consideration that the plane moves fast). So, motion is relative,
how fast you move depends on your perspective. Einstein added that things are
even more relative than this. Speeds is not only relative, but time is too. He says
that the speed of light is constant (speed=distance/time), if speed is constant and
the distance becomes longer (if your standing on earth), which means time moves
slower on the plane than on earth (time dilation). E.g. if you turn on a flashlight in
the plane towards the ceiling, it will be a straight line (you can calculate how long
it will take for the light to hit the ceiling). If a person on earth held a flash light
upwards towards the plane, the path of light beam will be different because in the
time that the light beam hits the ceiling of the plane from the flashlight, the plane
would have already moved to the right (which means the light beam moves
diagonally up and diagonally down). This was proven by atomic clocks placed in
the plane and on earth (which had a different time: 0.0000003s).
® You can also have the opposite effect, that distance is affected (length
contraction), the faster you move if you are in a plane that moves half the speed of
light, things will get half as big (from earths perspective). They will see the object
shrink because space will become contracted. The conclusion Einstein drew from
this is that time and space are moving particles. There is not separate time,
separate space. There is just one thing called space time that is flexible in a way
depending on your position.
® September 1905: Oh yes, by the way, E = mc2 (very heavy objects have the
property to bend space around it and this is what explains gravity). E.g. Einstein
says the sun is so heavy that the space around it curves.
Fixed notions like time and space are suddenly started to behave in a very strange way in
Einstein’s theory and this is also what worried the philosophers. E.g. they have done
philosophy of science for centuries and they believed Newton was right and Copernicus was
right and suddenly Einstein proved them wrong, which kind of resulted in a revolution for
philosophers. There was a confirmationist response to all of this. They were thinking what
should happen now since science can surprise us with the most counterintuitive results we
could imagine (having ideas about nature and time but being proven wrong).
Confirmationists = logical positivists
1. The confirmationists developed a ‘logical approach’ to fix this
® Developed by the Vienna Circle (or Wiener Kreis)
, ® A group of scientists that met regularly in the 1920s and 1930s to develop a new
philosophy of science.
® What was wrong was that we had too many assumptions about what the nature of
the world was like. There was no justification on the basis of what we observe.
We thought we could assume that space is like we see space, or that time is
moving forward with one second by second, but this was just an assumption
which was not justified on the basis of our scientific observations.
® They came up with the fact that we should try to prevent such scientific
revolutions in the future (how can we prevent that people in the future again prove
everything wrong).
® They came up with to spell out the logical structure of scientific theories (spell
out all the observations, conclusions we draw on the basis of those observations,
the conclusions we draw on the basis of those conclusions, etc.).
® They viewed a scientific theory as a system of sentences and reconstructs the
logical links between these sentences (is it induction/deduction, if it’s an
induction, how necessary is that conclusion on the basis of the observation, are we
sure that all those observations are actually true or maybe we saw something else).
In this way they want to prevent that you base your theory on assumptions that are
not justified (like Newton had done).
® In this way, they could determine the exact nature of our evidence.
® Example: You have a friend who lives in Amsterdam and you have agreed to pick
him up at 21.00 at Tilburg Central Station. When you arrive at the station, you
cannot find your friend. This surprises you because he is never late. Then you hear
from the announcer that the train from Amsterdam is delayed. You hypothesize
that your friend is still on his way
® If you really spell out all these assumptions and draw the logical connections
between these assumptions (theory of the confirmationists), then you will see
exactly whether or not your theory is justified on the basis of your observations.
