Comment by gnaritas

Correct, the goal: "To promote the Progress of Science and useful Arts", i.e. make trade secrets public, Science is a public endeavor, the goal here is the public good, not the inventors good. The means of obtaining that goal: " by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." They key word here is "by" which makes it clear we're now discussing means and not the goal. The goal is the first phrase of the sentence.