Paula Witlox, 2018
Samenvatting History of Modern Philosophy Hertentamen
Knowledge
Part 1: knowledge theories
The history of philosophy is not just a random succession of ideas and positions. It is a story that exhibits at
least some logical necessity and has made us who we are. This, in fact, is Hegel's view of the role of history. But
none of the other philosophers of early modernity would have really agreed. Understanding the history of early
modern philosophy requires us to understand the early modern's negative approach to history.
Aristotle took a positive approach to history, he was taking other philosophers’ theories and correcting the
errors and add own ideas. Later antiquity had the tendency for hero worshipping and the also the scholastics
took part in a form of tradition.
At the beginning of the 17 th century there was a radical break: philosophers suddenly rejected this conception
of history and came with a negative approach to history (Bacon and Descartes).
René Descartes
Cartesian skepticism: Perhaps all that we have learned is wrong. Therefore, we need a clean break with the
past so that we can grasp the full truth. Thus, Descartes tells us to doubt everything we can possibly doubt.
Then, when we have nothing in our minds except for what’s put there by nature, we can find out what truth is.
But is this possible; can we rid ourselves of everything we have ever learned and start out a new philosophy?
Descartes’ use of the ‘evil demon experiment’: I cannot doubt that I’m doubting if I exist, therefore I exist. If I
can prove that god exists and that god is supremely good and powerful, I can be sure that I am not deceived by
an evil demon. If I am not being deceived by an evil demon, then I can be sure my senses are to be trusted.
Proof of God’s existence: I find in myself the idea of a perfect being that is god. But, I myself am not perfect. An
imperfect being cannot create something perfect, so I could not have created the perfect being that
corresponds to this idea of god. Then there must have been a perfect being that created this perfect idea.
Therefore, god has to exist.
Does this even make sense? How can we start thinking if we have nothing to think about, because we haven’t
learned anything? Would you, for example, be able to come up with ethics on your own after a bad childhood?
We cannot think from nothing, we have to start from an historical situation (Hegel was right!). The entire early-
modern philosopher’s dream of starting from nothing and create a philosophy that is not based on anything, is
impossible.
Descartes starts with facing skepticism. He is not himself a sceptic, but he comes up with it to defeat it.
The most important doubt in Cartesian skepticism: the doubt that there might not be an external world. This is
called External world skepticism. Skepticism was nothing new, it was one of the big schools of philosophy in the
ancient world. Though not a single skeptic philosopher has ever brought up External world skepticism.
External world skepticism vs. ‘Five seconds ago’ skepticism: maybe the world only exists 5 seconds and we’re
only created in this moment, with certain “memories” of time. (no philosopher actually takes this seriously, but
why should we believe Descartes then?)
How is it possible that Descartes is the first philosopher to come up with skepticism about the external world?
Descartes had an innovating conception of the relationship between body and mind.
The ancient distinction between body and reason was the distinction between the temporal/the changing and
the eternal/the unchanging. The body is that what is temporal and the mind is that what is eternal.
For example, Augustine’s proof for the immortality of the soul. Augustine wants to prove that our rational
faculty (the mind) will survive death. There are eternal truths, like 1 + 1 = 2 and other mathematical facts. Also:
the good is always the good, not only today or tomorrow, so the good is eternal. His prove for the surviving of
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the rational mind is that if the rational mind can think of eternal things it has to be eternal itself. Ideas have to
be eternal things. For the ancient and medieval philosophers this is the distinction they make for material and
not-material things: to decide if they’re eternal or temporal
Descartes story of mind and body was very different of this ancient conception of mind and body. He uses a
new epistemological criterion. Namely: the dubitable vs the undubitable (stuff that you can’t doubt). The things
I don’t need evidence for, are the contents of my own mind. Feelings/ consciousness are the things I can really
be sure about. The Dubitable is the non-mental stuff.
Perception according to Descartes: a process that crosses from the mental to the Physical. If I can trust my
senses, I can trust perception. The step from the mental to the physical introduces the space for error.
For ancient thinkers this makes no sense at all, perception should be the activation of the sense organs, so it
should be a crossing from physical to mental. For example: “am I seeing a table?” That can be doubted; but it
cannot be doubted that I have a table-like impression in my consciousness. Perception moves from the realm
of the body to that of the mind; but by the same token, it stops being unproblematically a case of perception.
Between me and the world, there is now the veil of ideas.
Modern philosophers start reasoning from the inside. External world skepticism tells us this is actually
impossible. So, first modern philosophers have to “defeat” external world skepticism. This is where external
world skepticism becomes relevant; the central task of philosophy is to get object and subject together again
and make knowledge possible.
Of course, this has to be achieved from the side of the subject. Somehow, within the subject, we must find
uncontroversial evidence that our ideas accurately reflect an external reality. But how is this possible? This is
the driving question of early modern philosophy, and it will ultimately find its greatest and logical conclusion in
Kant.
According to Descartes, we cannot use perception to get knowledge, unless we can prove that the perception is
reliable. And of course, we cannot use perceptions to prove our perceptions are reliable.
For Descartes, it is finding the idea of God in ourselves that proves that our ideas do accurately reflect reality.
But he needs something to turn this idea into an external reality; and that something is precisely the
controversial assumption that this idea's existence implies the existence of that of which it is the idea.
Descartes denies this for everything else, but believes that it must hold for God – and that God can in turn
ensure it for everything else.
Rationalism and empiricism
Does all knowledge come from the senses? There are two main perspectives on this question. Empiricist claim
that indeed all knowledge comes from perception, but rationalists deny this claim.
If the empiricist wants to be a modern philosopher, he must say that in perception we automatically cross the
line to the external world. “Real things” than become equal to ideas, but this is not what he, as a modern
philosopher, wants. So, the empiricist has to become an idealist.
Berkeley’s esse est percipii: To be is to be perceived. For empiricists, the world is nothing above perceptions.
The object is part of the subject.
Hume’s idealism and skepticism about the continued existence of material objects (is the thing still there if
nobody’s perceiving it? If something is not in my perception, then it cannot be in the world either) and his
thoughts about stuff like causation (Causation doesn’t exist, because we can’t see/feel… it). If epistemological
primacy is given to the sensations of the subject, then the only way to bridge the gap to the objects is by
identifying the objects with the subjective sensations. Empiricism, for all its seeming links to science, has a
tendency to become a metaphysical idealism. This seems to be a problem for Berkeley, but Berkeley answers:
These are not actual problems, because God is perceiving everything all the time.
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Empiricism has now become an attempt to answer the central problem by collapsing the object into the
subject. There is a sense in which rationalism can be understood as the opposite: the attempts to collapse the
subject into the object. This is made possible by appealing to one special object: God.
Descartes, Spinoza, Leibniz; Hobbes, Locke, Hume – it's the rationalists that need God, and the empiricists that
can do without. (Berkeley is the apparent exception, but God plays a metaphysical role for him, not an
epistemological one.)
God is important, mostly because of the fact that God has all of his attributes necessarily. The senses tell us
about the contingent; reason tells us about the necessary. The price for rationalism is that everything must
become necessary, and God is the tool for making this happen. But, the proof of the existence of god seems to
be highly problematic, believe only is not enough.
Leibniz and the best of all possible world: Without God and his Goodness, there wouldn't even be any reason to
believe in the existence of anything outside of the monad that is me.
God is the object that determines everything; the object that I can know in advance; and thus the one road to
knowledge. But this means that everything depends on our philosophical knowledge of God... which is highly
problematic, as Kant, among others, would show. If it is problematic, it can’t be the solution to the central
question.
In short: empiricism and rationalism both run into really big problems. Empiricism cannot do justice to the
object, but has to identify it with sensation; rationalism cannot do justice to the subject, but has to appeal to
something external, God. Neither is able to solve the central problem that Descartes introduced.
However, both get something right about knowledge. Empiricism is surely right to say that we know about the
world through our senses. Rationalism is surely right to say that our senses alone are not enough. As Kant
famously puts it: “Thoughts without content are empty; intuitions without concepts are blind.” Kant will
attempt a synthesis between empiricism and rationalism. And as we already understand, this must involve a
new way of thinking about subject and object.
Immanuel Kant
Kant’s epistemology: Difference between kinds of knowledge, namely ‘A priori knowledge’ and ‘a posteriori
knowledge’ and a distinction between ‘analytic knowledge’ and ‘synthetic knowledge’.
- A priori knowledge: knowledge of which we don’t need evidence. Empiricist say all the knowledge of
the external world is a posteriori knowledge.
- A posteriori knowledge: knowledge that comes from the senses. Rationalist say some of our
knowledge is a priori knowledge.
- Analytic: A judgement where the predicate is already inside the object; the bold man has no hair. This
is always true: Knowledge that is true by definition
- Synthetic: not true by definition; the bold man is married.
All analytic knowledge is a priori: the pope is the head of the church. Another kind of knowledge is synthetic a
posteriori: there’s a bottle on the table. There is no knowledge that is analytic a posteriori, but what about
synthetic knowledge that is a priori?
“A straight line is the shortest route between two points.” This is not analytic; but it is not a posteriori either.
According to Kant, it is synthetic knowledge a priori.
Our knowledge in this case is based on our intuition of space. Apart from any specific spatial sensations, I can
check my pure intuition of space and find out that indeed a straight line is always the shortest route between
two points.
Now we come to the question that will generate Kant’s philosophy: how is such synthetic knowledge a priori
possible? If space is outside, how can my intuition, which is inside, be an infallible a priori guide to it?
Well, it can’t... unless the objects are constituted by the subject. An object is an object of knowledge and must
conform to the necessary conditions of experience. On the other hand, a subject is a knowing subject and must
be understood in relation to the objects that make up its world – e.g., this spatio-temporal body.
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