After a year of homeschooling prompted him to consider how much he actually knew and how he'd learned it, Robby Porter-builder, solar-panel-installer, ski-trail-groomer, woodworker, hydroelectric engineer, and philosopher-decided to write down everything he'd learned that he thought was worth knowing, and the result was this collection of essays both humorous and astute. Porter, who believes in Socrates' dictum "The unexamined...