The young Capote had already begun to work on stories. "I convinced [Harper] she ought to write too," he said later. "She didn't really want to but I held her to it."The issue here is with the word convinced. To quote Bill Bryson on the difference between convince and persuade:
Although often used interchangeably, the words are not quite the same. Briefly, you convince someone that he should believe but persuade him to act...Another distinction is that persuade may be followed by an infinitive but convince may not.So, in other words, you can convince people that Ben Affleck's acting is execrable, and they may be convinced of his execrableness, but you persuade them to avoid watching his "acting" in future films.
At least that is the pedantic grammar snob line. The American Heritage Dictionary, however, while noting that this is the "traditional rule," is more forgiving:
In a 1981 survey, 61% of the Usage Panel rejected the use of convince with an infinitive. But the tide of sentiment against the construction appears to be turning. In a 1996 survey, 74% accepted it in the sentence I tried to convince him to chip in a few dollars, but he refused.That's how it starts, you know. First you start using persuade and convince interchangeably; then, before long, you're impacting with reckless abandon, and eventually you lose all sense of restraint and become a self-indulgent, louche, besotted shell of your former self, living out your final years in a fog of gin fumes. Happens all the time. Just look at Truman Capote.
