William B. Irvine, author of the popular book 'A Guide to the Good Life,' offers much needed philosophical advice on how to become a more rational and critical thinker in today's emotionally-driven and complex world. Even the most reasonable of us can be selective about when we think reasonably. We may realize that the best thing to do is to take the advice of our doctor when facing a medical issue. When shopping for a new car or appliance we might carefully assess online reviews and weigh our options calmly before making an informed decision. But when it comes to things that feel more fraught --voting, navigating a challenge in our family, figuring out what to do in a difficult professional situation-- we might throw this approach out the window, dismissing facts and patterns that form a body of evidence, and trust our gut. (Of course, there is a time and place for this, but not every big decision is purely a matter of the heart.) Likewise, when we think about big ideas, about right