Scepticism
Colloquially, scepticism is identified with a dispositional state; that feeling of incredulity induced by some claim or set of claims. However, for our purposes, we will employ a more formal definition. Specifically: Scepticism about a certain proposition, P, means to withhold assent to P and to not P—i.e., to not take an affirmative or negative stance towards that proposition. So, to be sceptical of P is to imply something about the status of human knowledge: We don’t know whether P is the case.
In the interest of conceptual clarity, we want to pull apart three layers of scepticism that fall under the definition so described. Thereby, we can properly examine the justifiability of the sceptical stance. With each proceeding layer, what we can take as given, according to the sceptic, becomes increasingly scarce.
1. Local Scepticism (P = such-and-such a domain gets at the truth)
Local scepticism is that scepticism with respect to a particular domain. For example: one may be a sceptic in the moral domain, sceptical that we can know certain moral ‘truths’ (by intuition, perception, reason or otherwise); or, one may be a sceptic in the theological domain, sceptical that we can know the existence of a God (or set of Gods), considering all the relevant evidence. If we are to take on any given local scepticism, it’s variable the degree to which we must jettison our claims to knowledge. Indeed, the radicality of the scepticism will be a function of the domain in question. However, the barrier for entry is, in principle, relatively low. This is why we should call it the first layer.
2. Possible-World Scepticism (P = our perceptions represent the external world)
Possible-world scepticism (PWS) is that scepticism which suggests that we cannot know the nature of the external world. This is justified by ‘possible-world scenarios’, or ‘sceptical hypotheses’, which fall out of the following formula:
a. There is a possible world, x, which is consistent with your experience.
b. For any possible world which is consistent with your experience, you cannot know whether that possible world is the actual world.
c. Therefore, you cannot know whether the possible world x is the actual world x.
Examples: you're a brain-in-a-vat being fed experiences; you're in the dream of a higher self; you're being deceived about your experiences by an evil demon.
Using PWS, x can be such as to render the common-sense view of the world wholly misguided, and yet one can’t even bring probability statements to the table with which to evaluate x versus not x. From here, then, it’s argued: We cannot know whether the common-sense view of the world is true or false. PWS requires that we throw out basic assumptions, taken-for-granted in daily life: the objectivity of the external world, existence of other minds, and reliability of the senses. So, though technically PWS is local scepticism, it should hold a special, distinct place, forming our second layer.
3. Absolute scepticism (P= the set of all propositions)
Absolute scepticism is that scepticism which suggests that we can’t know anything (or pretty much anything), denying knowledge of much of what one takes to be self-evident. This may include:
Evaluating Each Stance
1.1 Naturally, people are open to local scepticism. This is the kind of scepticism involved in normal, critical thinking, and the word "gullible" is pejorative for good reason. If one aims not to undermine basic discourse, local scepticism is a valid and healthy scepticism.
2.1 PWS is less well-received. Most people bootstrap specific assumptions about the reality of the ‘out there’, that are unwelcoming of sceptical argument. There is certainly this intuition that: I’m looking at my desk, I see my desk, and I see my desk because there really is a desk there. Still, our intuitions on this point don’t survive scrutiny. Once one registers the fact that their experience, in a possible-world scenario, would be actually indistinguishable, in all respects, to how it is now, one sees that there’s simply no basis upon which to rule such a scenario out. Thus, I also lend credence to PWS.
Note: This scepticism is exactly that which claims we cannot know whether we’re living in a simulation, a fairly widely accepted possibility. We should recognise the generalisation which follows.
3.1 Regarding absolute scepticism, this is far and away from a live option for people! There’s not even much way of translating the philosopher’s talk into the common vernacular, here. For those who do encounter absolute scepticism, they do so not without great hostility—most want to say it’s self-contradictory, or an impossible position for an experiencing being to hold. Of course, that's fine. Personally, I am uncertain. Consider, for instance: That the absolute sceptic may presuppose the axioms he claims not to know when he justifies not knowing them, does not mean that we, now, have somewhere to stand from which to say that those axioms are known. And, when one starts "digging down" to their base claims to knowledge, one does encounters a kind of epistemic circularity. For me, it's this which invites doubt, but I leave it for the reader to decide.
Colloquially, scepticism is identified with a dispositional state; that feeling of incredulity induced by some claim or set of claims. However, for our purposes, we will employ a more formal definition. Specifically: Scepticism about a certain proposition, P, means to withhold assent to P and to not P—i.e., to not take an affirmative or negative stance towards that proposition. So, to be sceptical of P is to imply something about the status of human knowledge: We don’t know whether P is the case.
In the interest of conceptual clarity, we want to pull apart three layers of scepticism that fall under the definition so described. Thereby, we can properly examine the justifiability of the sceptical stance. With each proceeding layer, what we can take as given, according to the sceptic, becomes increasingly scarce.
1. Local Scepticism (P = such-and-such a domain gets at the truth)
Local scepticism is that scepticism with respect to a particular domain. For example: one may be a sceptic in the moral domain, sceptical that we can know certain moral ‘truths’ (by intuition, perception, reason or otherwise); or, one may be a sceptic in the theological domain, sceptical that we can know the existence of a God (or set of Gods), considering all the relevant evidence. If we are to take on any given local scepticism, it’s variable the degree to which we must jettison our claims to knowledge. Indeed, the radicality of the scepticism will be a function of the domain in question. However, the barrier for entry is, in principle, relatively low. This is why we should call it the first layer.
2. Possible-World Scepticism (P = our perceptions represent the external world)
Possible-world scepticism (PWS) is that scepticism which suggests that we cannot know the nature of the external world. This is justified by ‘possible-world scenarios’, or ‘sceptical hypotheses’, which fall out of the following formula:
a. There is a possible world, x, which is consistent with your experience.
b. For any possible world which is consistent with your experience, you cannot know whether that possible world is the actual world.
c. Therefore, you cannot know whether the possible world x is the actual world x.
Examples: you're a brain-in-a-vat being fed experiences; you're in the dream of a higher self; you're being deceived about your experiences by an evil demon.
Using PWS, x can be such as to render the common-sense view of the world wholly misguided, and yet one can’t even bring probability statements to the table with which to evaluate x versus not x. From here, then, it’s argued: We cannot know whether the common-sense view of the world is true or false. PWS requires that we throw out basic assumptions, taken-for-granted in daily life: the objectivity of the external world, existence of other minds, and reliability of the senses. So, though technically PWS is local scepticism, it should hold a special, distinct place, forming our second layer.
3. Absolute scepticism (P= the set of all propositions)
Absolute scepticism is that scepticism which suggests that we can’t know anything (or pretty much anything), denying knowledge of much of what one takes to be self-evident. This may include:
- The laws of logic.
-Law of identity: Everything is identical to itself, a=a
-Law of contradiction: Something cannot both be and not be, ~( a & ~a)
-Law of excluded middle: Something either is or is not, a v ~ a - Theories of meaning (that the statements we make are meaningful).
- Rules of inference (e.g. if p then q, and p, then q).
Evaluating Each Stance
1.1 Naturally, people are open to local scepticism. This is the kind of scepticism involved in normal, critical thinking, and the word "gullible" is pejorative for good reason. If one aims not to undermine basic discourse, local scepticism is a valid and healthy scepticism.
2.1 PWS is less well-received. Most people bootstrap specific assumptions about the reality of the ‘out there’, that are unwelcoming of sceptical argument. There is certainly this intuition that: I’m looking at my desk, I see my desk, and I see my desk because there really is a desk there. Still, our intuitions on this point don’t survive scrutiny. Once one registers the fact that their experience, in a possible-world scenario, would be actually indistinguishable, in all respects, to how it is now, one sees that there’s simply no basis upon which to rule such a scenario out. Thus, I also lend credence to PWS.
Note: This scepticism is exactly that which claims we cannot know whether we’re living in a simulation, a fairly widely accepted possibility. We should recognise the generalisation which follows.
3.1 Regarding absolute scepticism, this is far and away from a live option for people! There’s not even much way of translating the philosopher’s talk into the common vernacular, here. For those who do encounter absolute scepticism, they do so not without great hostility—most want to say it’s self-contradictory, or an impossible position for an experiencing being to hold. Of course, that's fine. Personally, I am uncertain. Consider, for instance: That the absolute sceptic may presuppose the axioms he claims not to know when he justifies not knowing them, does not mean that we, now, have somewhere to stand from which to say that those axioms are known. And, when one starts "digging down" to their base claims to knowledge, one does encounters a kind of epistemic circularity. For me, it's this which invites doubt, but I leave it for the reader to decide.