In the example 8, Obama said "you" and "your" for five times to refer to the public. There is a difference between the status of Obama and the public. Obama, at that time, was the would-be president and the public would be under his leadership. The use of YOU helps to illustrate this difference. Moreover, Obama used "you" to change the focus of the campaign. According to him, the focus of the campaign is not his personal benefits but the benefits of the public. After hearing this, the public will feel that Obama do concern for them and as a result, they will trust him.

2.4 Discussion
Based on the researches made by the other scholars in the field of personal pronouns, Rees put forward the personal pronouns continuum showing every personal pronoun’s distance from self I . The closer a personal pronoun is to "I", the more subjective it is.
(indefinite)
Distance from Self
Rees’ Personal Pronouns Continuum
(Cited from Akinbiyi Adetunji, 2006:180; Rees, 1983: 16)

Above figure shows the word "we" ,followed by "you", is the closet to the self "I" ; while "they" is the farthest. The difference between the distance has a reflection in Obama’s speeches. By using HyConc, a software designed to analyze text, the person deixis frequency of the speeches analyzed in this paper is shown in the following table.      Personal Pronouns
Speeches    I    we    you     they
Declaration of Candidacy    43    61    22    11
Speech Against The Iraq War    18    4    6    0
The Audacity of Hope    29    36    7    25
Change Is Coming to America:Iowa Caucus Night    17    31    25    4
This Is Your Victory: Election Night    31    47    22    5
Financial Crisis Requires Action    92    96    59    24
I Will Accept This Award as A Call To Action    11    2    2    1
Total Amount    241    277    143    70
Rank    2    1    3    4
 The Frequency of Personal Pronouns in Some Speeches
According to the above table, we can see "we" is the most frequent personal deixis followed respectively by "I", "you" and "they". Obama considers the relationship between himself and the listeners a lot so he chooses carefully among"I", "we" and "you". There are usually two kinds of situations, in the first one, he should separate his president identity from the identity of being a normal person. In the second situation, he needs to shorten the relationship between him and the public, so that he can establish a common ground and appeal the audience’s emotion to follow him. No matter in what kind of situation, the use of "we" and "you" helps the audience to engage in the speeches rather than only listen to the speeches.

We can consider the use of first and second person pronoun as one of pragmatic strategies used by Obama in accordance with the Politeness Principle. According to the Agreement Maxim of Politeness Principle, the speaker should "minimize disagreement and maximize agreement between self and other". In the situation of public speaking, "self" refers to Speaker, and "other"refers to the Hearer. The use of "we" and "you" makes a serious speech conversational. In this way, the audience will have a sense of participation and the relationship between the speaker and the listener is shortened. Unconsciously, a common ground will be established and the audience will find similar points with addressee. Obama successfully used this strategy to achieve his communication goals. 浅谈奥巴马演讲中的语用策略(7):http://www.751com.cn/yingyu/lunwen_1567.html