  A noncooperative differential (dynamic) game model of opinion dynamics is
proposed. In this game, the agents' motives are shaped by their expectations of
the nature of others' opinions as well as how susceptible they are to get
influenced by others, how stubborn they are, and how quick they are willing to
change their opinions on a set of issues in a prescribed time interval. These
motives are independently formed by all agents. The existence of a Nash
equilibrium in the network means that a collective behavior emerges out of
local interaction rules and these individual motives. We prove that a unique
Nash equilibrium may exist in the game under quite different circumstances. It
may exist not only if there is a harmony of perceptions among the agents of the
network, but also when agents have different views about the correlation among
issues. The first leads to an accord in the network usually expressed as a
partial consensus, and the second to a discord in the form of oscillating
opinions. In case of an accord, the harmony in the network may be in the form
of similarity in pairwise conceptions about the issues but may also be an
agreement on the status of a "leader" in the network. A Nash equilibrium may
fail to exist only when the network is in a state of discord.
