First of all pluralism is a political philosophy and it is the affirmation of diversity within a political entity, that will provide the peaceful co-existence of the different lifestyles, interests and conviction.

According to the pluralist theory of government, we can say that decision making & politics are vested mostly in the hands of government.

Now lets look what is legitimacy of goverment... Political legitimacy of the government is from an agreement between the autonomous institutions, that is as you all know that they are, legislative, judicial & executive. And these three are combined together for the betterment of national. We all took part in elections. That election is the main way that we the society grants legitimacy to the goverment.