what does "lose one's purchase"here mean? what does "purchase"mean? The earliest signs of problems with his memory appeared about four years before. There would be times when he found it difficult to summon up the name of someone he knew well. Now and then, he’d also lose his purchase on a set of facts with which he wanted to support an argument. At other times, he’d briefly lose his sense of continuity in the course of what was otherwise a cogent conversation.