Philosophy 024: Big Ideas
Prof. Robert DiSalle (rdisalle@uwo.ca)
Talbot College 408, 519-661-2111 x85763
Office Hours: Monday and Wednesday 12-2 PM
Course Website:
http://instruct.uwo.ca/philosophy/024/
Certainty and Skepticism: some basic questions
(skepticism: from the Greek , to examine, inquire)
Can any human belief or perception be placed beyond doubt?
Once the possibility of doubt has been admitted, can it ever
be removed? Can any beliefs still be justified as knowledge?
Are there any beliefs that are worthy of being accepted as
foundations for other beliefs or inferences?
Can a genuine distinction be made between appearance and
reality?
Can skepticism itself be a consistent point of view?
Some basic skeptical and non-skeptical attitudes:
Dogmatic skepticism: Nothing can be known. Nothing is true.
All human claims to knowledge are false.
Pyrrhonian skepticism: Certainty is impossible, so the wise
person should suspend judgment about theoretical matters.
Empiricist foundationalism: The senses provide the ultimate
criteria for justifying belief.
Rationalist foundationalism: The senses give subjective or even
deceptive appearances, and only reason provides a foundation
for certain knowledge.
Authoritarianism: Certain persons (e.g. priestly authorities,
authors of sacred books) are empowered to know and to speak
the truth on fundamental matters.
Some underlying principles of skepticism
Relativity of perception:
Perceptions vary according to circumstances of
-- time and place,
--physical conditions,
the nature of the object, and
the nature of the individual perceiver.
Conclusion: Contrary to the empiricist, our own immediate
sensations are no guide to objective circumstances.
The problem of infinite regress:
Any rational argument must depend on premises. And these
premises must be deduced from other premises. And those most
be deduced from still other premises. And so on and on…
Or, the problem of conventionalism:
In order to avoid an infinite regress, we can simply choose a
principle as an axiom, and so refuse to justify it. But since the
axiom cannot be deductively justified, it is arbitrary.
Conclusion: Contrary to the rationalist, reason cannot provide a
foundation for true belief.
The problem of human variability and frailty:
For every opinion held by any reputable human being, there is a
contrary opinion that has been held by equally reputable human
beings.
Every opinion that now seems foolish has been, at some other
time or place, regarded as absolute truth by reputable authorities.
Generally, what human beings regard as certain varies according
to history and culture.
Conclusion: Contrary to the authoritarian, no human beings can be
regarded as having some special insight into the truth.
Montaigne: Skepticism to mitigate doubt
Credulity: Excessive trust in reports of others
Incredulity: Excessive confidence in the wisdom of one’s own
judgment.
Skepticism: a sense of the fallibility of human judgment
“We must bring more reverence and a greater recognition of our
ignorance and weakness to our judgment of nature’s infinite
power….For to condemn [improbable things] as impossible is
rashly and presumptuously to pretend to a knowledge of the
bounds of possibility.”
Descartes: “Discourse on the Method of Rightly
Conducting One’s Reason and Searching for Truth
in the Sciences”
“I do not intend to teach [the method], but only to speak about
it. For as you can see from what I say of it, it consists more in
Practice than in Theory, and I called the treatises…Essays in
this Method, because I hold that the things that they contain
could not have been discovered without the method, and that
through them you know its value.”
Discourse on the Method: An analytic method of
distinguishing truth from falsehood, and of building scientific
knowledge on secure foundations
Optics: A mathematical theory of the reflection and refraction
of light, including the discovery of the Law of Refraction
Geometry: The invention of modern analytical geometry,
including the reduction of geometrical curves and figures to
algebraic relations
Meteorology: A study of atmospheric phenomena, including a
derivation of the colours of the rainbow from principles of
optics.
(Descartes, 1637)
Rules of the “Cartesian method”:
Accept nothing as true except what is apprehended so clearly and
distinctly as to be beyond any doubt.
Divide each difficulty into as many separate parts as is possible
and necessary to resolve them.
Begin with the objects that are the simplest and the easiest to
know, and gradually ascend to the most complex and difficult-even assume such an order if none exists naturally.
Make such a complete review and enumeration, at the end, as to
be sure that nothing important has been omitted.
Leibniz’s gloss: “Take what you need and do what you must, and
you will get what you want.”
The Cartesian skeptical method (“radical doubt”):
Turning doubt against itself
What would happen if I systematically attempted to doubt
absolutely everything?
Could such an attempt really succeed?
Or would I discover that there are certain principles that it is
absolutely impossible to doubt?
If I begin by treating all my ideas as false, will I discover that my
mind contains ideas that bear unmistakable marks of truth?
(Descartes, Meditations, 1641)
Cogito ergo sum: “I think, therefore I am.”
“While I wished to think that everything was false, it
was necessarily the case that I, who was thinking this,
was something.”
“…this truth, I think, therefore I am, was so firm that
all the most extravagant assumptions of the sceptics
were unable to shake it…”
“…from the very fact that I was thinking of doubting
the truth of other things, it followed very evidently and
very certainly that I existed….”
Now that we know one certain truth, we ask, in what
does its certainty consist? What rule can be developed
for recognizing certain truths?
Nothing convinces Descartes of the truth of “Cogito,
ergo sum,” except the fact that he clearly and distinctly
perceives it to be true.
Therefore “I could adopt as a general rule that those
things that we conceive very clearly and distinctly are
true. The only outstanding difficulty is in recognizing
which ones we conceive distinctly.”
Can ideas have “marks” that tell us whether they
correspond to something real?
Descartes: From my doubts I know that I am limited and
imperfect.
But the idea of God has such perfection in it that I know that its
cause must be something outside of me, i.e., a perfect being.
Nothing in any other idea implies the existence of the
corresponding thing. I can be certain of the properties of a
triangle, but nothing I can know about the essence of a triangle
can tell me whether there is such a thing as a triangle.
But the idea of God contains existence in its essence. That God
exists is as certain as that a triangle has three sides.
(Ontological Argument)