I'm very happy to see you writing (so well) about the summum bonum.
I don't have the text of Sextus at hand to cite you chapter & verse, but I think I recall this correctly.
It would be pretty ironic for a skeptic to denigrate inquiry since skeptikos means precisely one who inquires. The skeptic arrives at adoxia (if he does) not by deciding or choosing to walk away from an issue like AGW [anthropogenic global warming], but by inquiring into it assiduously. If he does so, then something begins to happen in his mind as he accumulates many many arguments pro and con. He eventually finds himself in a state of equipoise, as inclined to believe as to disbelieve. Adoxia is the spontaneous product of assiduous inquiry.
Slim is alluding to, and taking issue with, the last sentence of Ataraxia and the Impossibility of Living Without Beliefs. What I said there implies that the Pyrrhonian denigrates inquiry. Slim rightly points out that the skeptic is by his very nature an inquirer. And as I myself have said more than once in these pages, doubt is the engine of inquiry. So my formulation was sloppy. It is not that the skeptic denigrates inquiry; it is is rather that he denigrates the notion that inquiry will lead to a truth that transcends appearances.
The Pyrrhonian skeptic inquires, not to arrive at the truth, but to achieve doxastic equipoise and adoxia, belieflessness. This in turn is supposed to engender ataraxia.
It's a bold conjecture, and, alas, a completely false one, in my experience at least. The more I inquire into an issue, the more likely I am to settle on one side or another, and not find myself floating in tranquil equipoise betwixt them. Maybe your experience is different? In any case, the skeptical remedy for partisan belief is study, study, study. They believe studying something to death will take you to equipoise and ataraxia. Willfully choosing to ignore an issue like AGW, they believe, will not buy you ataraxia at all. You remain disposed to believe or disbelieve according to your prejudices, and only the therapy of inquiry can work these doxastic prejudices out of you.
Slim here offers an excellent and accurate summary of The Skeptic Way, which is also the title of a fine book by Benson Mates.
One can doubt whether ataraxia is the summum bonum and whether it is achievable in the skeptic manner. But one thing to me is clear: insight into just how inconclusive are the arguments on both sides of many if not all issues leads to a salutary decrease in dogmatism.
John Lennon bade us "imagine no religion." But why single out religious beliefs as causes of conflict and bloodshed when nonreligious beliefs are equally to blame? Maybe the problem is belief as such. Can we imagine no beliefs? Perhaps we need to examine the possibility of living belieflessly. In exploration and exfoliation of this possibility we turn to the luminaries of late antiquity.
A concept central to the Greek Skeptics, Stoics, and Epicureans, ataraxia (from Gr. a (not) and taraktos (disturbed)) refers to unperturbedness, freedom from emotional and intellectual disturbance, tranquillity of soul. Thus Sextus Empiricus (circa 200 Anno Domini) tells us in his Outlines of Pyrrhonism, Book One, Chapter Six, that "Scepticism has its arche, its inception and cause, in the hope of attaining ataraxia, mental tranquillity." (Hallie, p. 35) The goal is not truth, but eudaimonia (happiness) by way of ataraxia (tranquillity of mind). The central means to ataraxia and happiness is the suspension (epoche) of beliefs, not all beliefs, but those that transcend the mundane and give rise to contention and strife. To use some contemporary examples, beliefs about abortion, gun control, capital punishment, wealth redistribution, illegal immigration, foreign policy, the nature and existence of God etc. lead to strife and in extreme cases bloodshed. Given the difficulty and seeming irresolvability of the issues, the skeptic enjoins suspension of belief for the sake of ataraxia.
Now freedom from disturbance is clearly good, but is it the highest good? Is the highest life the beliefless life, the life that strives after the highest attainable degree of suspension of belief in respect of contentious matters?
One question is whether it is even possible to live without contention-inspiring beliefs. If it is not possible, then the beliefless life cannot be an ideal for us. 'Ought' implies 'can.' If we ought to do something, then it must be possible for us to so it. The same holds for ideals. Nothing can count as a genuine ideal for us unless its realization is at least possible by us. Now I have argued elsewhere that not even the skeptic can avoid some contention-inspiring doxastic commitments. So I maintain the view that the beliefless life is not possible for us and hence not an ideal for us either.
But even if the beliefless life were possible for us, it would still not be choice-worthy. For our very survival depends on our knowing the truth about matters difficult to discern. For example, is global warming real, and if it is does it pose a threat to human survival? What about the threat to civilization of militant Islam? How much of a threat is it?
These two issues are extremely contentious. Acrimonious and ataraxia-busting debate rages on both sides of both of these issues. But obviously it does matter to the quality of our lives and the lives of our children and other world-mates what the truth is about these questions. It certainly made a difference to the quality of the lives of the workers in the Trade Towers on 9/11 that militant Islamofanatics targeted them. Their quality of life went to zero. Just one bomb can ruin your entire day.
So how could it possibly be right to say that the highest life is the life of belieflessness? If I suspend belief with respect to every contentious matter, every matter likely to induce mental perturbation, not to mention bloodshed, then I suspend belief with respect to the Islamofascist threat. But then I show indifference to my own well-being. It doesn't matter whether you agree with me about the threat of militant Islam. Perhaps you are a leftie who thinks that global warming is more of a threat. Then run my argument using that example.
Mental tranquillity is a high value, and no one who takes philosophy seriously can want not to possess more of it. But it cannot be the highest value. The happy life cannot be anything so passive as the life of ataraxia. We need a more virile conception of happiness, and we find it in Aristotle. For the Stagirite, happiness (eudaimonia) is an activity (ergon) of the soul (psyche) in accordance with virtue (arete) over an entire life. His is an active conception of the good life even though the highest virtues are the intellectual virtues. The highest life is the bios theoretikos, the vita contemplativa. Though contemplative, it necessarily involves the activity of inquiry into the truth, an activity that skepticism, whether Pyrrhonian or Academic, denigrates.
Benson Mates, The Skeptic Way, Oxford UP, 1996, p. 5: ". . . the characteristic attitude of the Pyrrhonists is one of aporia, of being at a a loss, puzzled, stumped, stymied." Aporia is not doubt. Doubt implies understanding, but aporia is a lack of understanding. The modern skeptic may doubt, but not the ancient skeptic.
Connected with this is a distinction between epoché as the withholding of assent and suspension of judgment. One can withhold assent from an assertion without granting that it makes sense; but if one suspends judgment then one has a clear propositional sense before one's mind which one neither affirms nor denies. See Mates, p. 32. A good distinction! Add it to the list.
So, strictly speaking, aporia is not doubt and epoché is not suspension of judgment. Close but not the same.