By B.P. Morton
[The sun came up with no conclusions ...] Skepticism is typically associated with epistemological concerns. Humans seem to have limits. These limits seem to effect what we can legitimately know. Ergo there are things we cannot know with as much certainty or justification as we might like. We can haggle about the scope of our limits and knowledge, about the details of our knowing and lack of knowing. There are many details to be filled in. The skeptic can list long sets of “modes” or standardized arguments for lack of knowledge. The epistemic optimist can try to overcome them. Rinse, lather, repeat. And there are plenty of ancient modes and arguments to examine, and plenty of more recent ideas (about say cognitive bias results, or the neuroscience of the timing between brain activation and the feeling of making a decision) that can easily be fashioned into new modes.
But as Hilan Bensusan recently pointed out, it's possible to read some skeptics as having motivations that go beyond the epistemic. Aenesidemus can be read as worrying that reality doesn't provide the right background for human knowledge, that the world is “in a flux, multiple, mixed and undetermined.” And this worry builds bridges between a skeptic like Aenesidemus, and various near skeptical positions like say Heraclitus or the Mahavira. And once you open the can of worms, I think it is clear that there are many examples here. You can motivate skeptic or near-skeptic positions from metaphysics rather than epistemology, but I think you can also do so from ethics or logic or even aesthetics. Skepticism is a stream of philosophy into which, many quite different sets of motivations flow.