On the strength of these profound views, he in the most ingenious manner takes infinite pains to counterplot when there is no plot, and plays the deepest games of chess without any adversary.
I was sufficiently engaged during the remainder of the evening in taking my first lesson in backgammon from Mr. Jarndyce, who was very fond of the game and from whom I wished of course to learn it as quickly as I could in order that I might be of the very small use of being able to play when he had no better adversary.
There are no more uses of "adversary" in the book.
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Then, again, our military training is in many respects superior to that of our adversaries.
Thucydides -- Pericles’s Funeral Oration
Finally, it was rumored, there would be complete information-sharing among all of these previously disconnected and even adversarial entities, and when they were coordinated, and once all the health data they’d collected was shared, most of this made possible through the Circle and more important, TruYou, viruses could be stopped at their sources, diseases would be tracked to their roots.