It was David Hume, in the 18th century, who showed how to bring scepticism back to life. The first step is to keep in mind what Hume called the "strange infirmities" of human understanding, and the "universal perplexity and confusion, which is inherent in human nature". Armed with this knowledge—for our ignorance is the one thing of which we can be certain—we should be sure to exercise the "degree of doubt, and caution, and modesty, which, in all kinds of scrutiny and decision, ought for ever to accompany a just reasoner". Apart from anything else, this would help to cure people of their "haughtiness and obstinacy".
In theory, we have all learned Hume’s lesson, because a modest scepticism is the official philosophy of the modern sciences, which avow the maxim that every result is to be probed, repeatedly, and no truth may be admitted until it has stood the test of time. But, in fact, we have not learned his lesson. Nobody has time to wait and see whether yesterday’s experiment will still stand several decades from now. Life is short and writers have deadlines. So scepticism is a philosophy that is not easy to live up to. But who would want a philosophy that was?
For most of us, if we're honest, we have to admit that much of our "knowledge" has been bought with cheap credit from potentially unreliable intellectual lenders, liable to come crashing down if subjected to rigorous scrutiny. And so I'm tempted to agree with Gottlieb's opinion that Hume's philosophy is the "best" all-around. In his Enquiry Concerning Human Understanding, Hume said something that I've always found practically useful: "And here it is constantly supposed that there is a connexion between the present fact and that which is inferred from it." Training yourself to be keen to those faulty or nonexistent "connexions" will keep you busy for as long as you're willing, and possibly even make you look much smarter than you really are.