skepticism Flashcards
Skepticism
the view that many/most of the things that we take ourselves to know we do not in fact know
global skeptic
A global skeptic will maintain that we do not know anything
local skeptic
A local skeptic, on the other hand, will maintain that we don’t know any truths within some particular
domain
skeptic arguments
most arguments within skepticism are skeptic scenarios
The first thing to note about these scenarios is that, in some sense, they seem possible
The skeptic starts from the thought that there are such possible skeptical scenarios and tries to use this fact to argue that we then don’t know certain facts that we take ourselves to know
One feature of the skeptical scenario that is striking is that in the scenario everything seems the way it actually does, and yet things are in fact radically different
skeptical argument 1
(P1) If in situation S1 you have exactly the same evidence as in situation S2, then you know P in S1 just in case you know P in S2
(P2) In the brain in a vat scenario (BIV) you have exactly the same evidence as the the actual situation (A)
(P3) In (BIV) you do not know that you are sitting in a room
(C) In (A) you do not know that you are sitting in a room
To reject (P2), then, you must maintain that you in fact have different evidence in (A) than you do in (BIV) - Indeed, one might maintain that in (A), though not in (BIV), it’s part of your evidence that you are
sitting in a room
One worry for this approach is that we need to allow that two scenarios can be subjectively indistinguishable, in an appropriate sense, and yet
one may have different evidence in the two cases
In the good case (A), there are propositions that are part of your evidence that aren’t part of your
evidence in the bad case (BIV)
But this difference in your evidence is, in some sense, not something that you can tell when you’re
in the bad case
To deny (P1) we would need to maintain that there is something, in addition to your evidence, that
determines whether or not you know something - the additional thing could be facts
The fallibilist will reject (P1).
They will allow that you do have the same evidence in (BIV) and (A). The evidence that you have is compatible with both scenarios
Thus the evidence that you have is compatible with the claim that you are sitting in a room and with the
claim that you are a brain in a vat.
the evidence suffices for knowing that we’re sitting in this room, when we have that evidence and, in fact, we are sitting in this room
valid argument
if the premisses are true, then the conclusion is guaranteed to be true
fallibilism
According to fallibilism you can know P even if your evidence is compatible with the falsity of P
What’s required for knowledge, on this view, is (perhaps amongst other things) that you have such evidence and that P be the case
the skeptical conclusion
If two scenarios are subjectively
indistinguishable, then one’s evidence is the same in both
If you have the same evidence in two scenarios then know the same things in those two scenarios
skeptical argument 2
When you present the brain in a vat hypothesis it’s natural to think: yeah I guess I can’t completely rule that out…or yeah I guess I don’t know that I’m not a brain in a vat.
Nonetheless, it also seems that we know lots of mundane things. For example I know that I have hands
The next skeptical argument tries to leverage the first thought to undermine the second
(P1) If you know P, and you know: if P, then Q, then you know Q
(P2) You know that if you have hands, then you are not a brain in a vat
(P3) You do not know that you are not a brain in a vat
(C) You do not know that you have hands
epistemic sensitivity
We say that a belief that P is sensitive just in case were P not true you would not believe P
some think that sensitivity provides a necessary condition for knowledge.
Sensitivity: If A knows that P, then A’s belief that P is sensitive
Assuming sensitivity it follows that I do not know that I’m not a brain in a vat. For if I were I brain in a vat, I would still believe (falsely) that I am not a brain in a vat.
But note that even though this is true, I can still count as knowing that I have hands, since this belief is sensitive
to resist the skeptical argument, we must
(i) Allow that there are some cases in which A knows P and A knows that if P then Q, and yet A does not know Q (even though A may competently
deduce Q from P)
(ii) Allow that you can rule out being a brain in a vat just by looking, despite the fact that that’s how things would look were you a brain in a vat
The Moorean Response
How do I know I’m not a brain in a vat
Well, look, here’s one hand, here’s another…since I have hands, it follows that I’m not a brain in a vat
Moore here is assuming a principle that our skeptic appealed to
Closure: If A knows P, and A knows if P then Q and A competently deduces Q, then A knows Q
The skeptic and Moore agree about the following: either (i) we know that we have hands and that we aren’t brains in vats, or (ii) we don’t know that we have hands, and we don’t know that we aren’t brains in vats
No argument, according to Moore, should convince us that this isn’t true. For any such argument must appeal to premisses that are less plausible that the claim that we know that we have hands
Closure
If A knows P, and A knows if P then Q and A competently deduces Q, then A knows Q
