I’m always leery of the term “outsider art,” which seems to be making allowances even before you push through the gallery doors. Whether decorative, devotional, or obsessive, such works aren’t necessarily intended for public display or sale. If anything, they can be too inside—hermetic and private in a way that excludes MFA interpretations and appreciation. Happily, none of those qualifications are necessary with the large, colorful drawings of Gregory Blackstock, the autistic-savant former dishwasher who gained local prominence about a decade ago. A shy, gray-haired gentleman who was playing accordion during this month’s First Thursday reception, he’s a cheerful explainer. His mostly tabular, annotated works are didactic in a sense; he’s teaching us something about flags and dogs and donkeys and hydroplanes, organizing and categorizing them for our edification. They’re like the rare color pages you find in an unabridged dictionary, illustrated not for the sake of art but instruction. There’s a comprehensive quality to them that falls short of the unsettling compulsion you see in Henry Darger, for instance, and some religious art. Blackstock is a maker of elaborate, illustrated lists. It doesn’t matter whether he means them to be art. What makes them so appealing is their sincerity and generosity—the way Blackstock shares his knowledge and enthusiasm with us.