First I introduce myself, Hilan, as this is my first post around here. I was invited to be part of this percs bunch blog about a month ago, and I'm very grateful for this.
I've been lecturing epistemology for the first time in two years and I'm enjoying my take. I started out analyzing Linda Zagzebski's claim that we are now in an askeptical period, where doubts and credentials are not cutting much ice in philosophy. We then moved to the nature of doubts and determinations and now we're in Sextus. I'm covering Aenesidemus' 10 modes and then Agrippa's 5. But I'm doing that contrasting Sextus use of the modes with the probably more askeptic use of Aenesidemus and of Pyrrho himself. The modes, read in this last way, are strategies to conceive the world as being in a flux, multiple, mixed and undetermined. In my forthcoming book (Being Up For Grabs, to appear in the New Metaphysics Series) I contrast Neopyrrhonism (Sextus' position) with what I label ontologies of doubt. The latter are committed to the idea that doubts and indeterminacies are in the world and not symptoms of our distance from a determined world. The modes then can be read as arguments about reality, claiming that, say, things are neither quite like I see them (3rd and 4th modes), nor quite like humans see them (1st mode) not because I cannot know how they are but rather because they reveal themselves as being more complex - and, in a sense, more doubtful (things are indeterminate, they are themselves unreliable).
The 5th mode is specially fruitful. Sextus writes that it
[...]is the one depending on positions and intervals and places - for depending on each of these the same objects appear different. For example, the same colonnade appears foreshortened when seen from one end, but completely symmetrical when seen from the middle. The same boar appears from a distance small and stationary, but from close at land large and in motion. [...L]amplight appears dim in sunlight but bright in the dark. [...] Coral appears soft in the sea but hard in the air.[...] Doves' necks appear different in color depending on the different ways they turn them. (Outlines of Scepticism, Annas & Barnes (ed.), Cambridge UP 2000)
I also added Heraclitus 3rd fragment (The sun is the size of my foot) just to relate to Sextus accusation that Aenesidemus ended up straying from the good skeptical path to adopt a Heraclitean dogma. In all those cases, the bite of the 5th mode is that any decision concerning whether the sun is greater than my foot would require choosing a reference point (maybe privileging places closer to the sun). From the point of view where I take my sunbath, my foot is quite larger than the sun. Only if a privileged position is assumed, the sun and my foot work fully as substances with properties that can be compared without indexes. The fifth mode points towards the position-dependent of relations - and the indexicality of qualities. It ushers in the idea that indexes and positions are widespread, although often concealed by a language of substances. I always think there is much to the closing paragraphs of Perry's "The problem of essential indexical" (Nous, 1979) where he says that the implicit nature of much indexicality is what gives the impression that de re beliefs are not the rule. Perry, of course, is arguing that beliefs are far more indexical than it is often thought. It is, therefore, in line with the 5th mode, and with a Sextus reading of it. But also Perry's remark could be read as being about the world: qualities and relations are often themselves de re and there is no sense in comparing the size of my foot and the size of the sun simpliciter. It is not that truth is relative to positions and indexes, it is rather that we ought to make sense of the claim that positions and indexes are true.