第一個用法，也就是在GMAT中常出現的  -  用在indirect speech （report speech）- 也就是說信息提供的人不是直接的陳述者。如human beings are thought to have first entered the Americans  大全325題
human beings first entered這個觀點不是這篇文章的作者這么想，而是 are thought（被認為 – 被人們認為）

因為to have 是用在indirect speech，所以經常跟在think, claim, believe 等于陳述信息相關的單詞后面多以被動的形式出現. To 前面動詞的事態沒有限制

可以從以下的例子中仔細體會 – 例子是從CD 的貼子中借的，都是大全例的例子

     it is thought to have happened

     six teenagers    claimed to have had vision of the virgin

     it is believed to have been the largest 

     few people are known to have recovered

     thought by some scholars to have occurred

     alleged to have been worn

經典的例子是大全157題，同時包括 to have 和 to be

Balzac drank more than fifty cups of coffee a day and died of caffeine poisoning; furthermore, caffeine did not seem to bother Samuel Johnson, the great writer and lexicographer, who was reported to have drunk twenty-five cups of tea at one sitting.

(A) furthermore, caffeine did not seem to bother

(B) however, caffeine did not seem to bother

(C) however, caffeine did not seem to have bothered

(D) furthermore, caffeine did not seem to have bothered（B）

(E) in addition, caffeine did not seem to bother

做這個題的時候有些朋友可能看到沒有劃線部分的have drunk 后根據平行原則選C， 但這里因為seem 不是表達別人意見的詞，而是做著對這件事情的看法，所以就沒有必要用to have bothered 正確 答案是B. 如果我們把句子改稱

however, it is said caffeine did not to have bothered 這樣就可以了

而沒有劃線部分who was reported to have drunk twenty-five cups of tea at one sitting注意一下這里的was reported 也就是 drunk twenty-five cups of tea at one sitting 這個表述不是作者直接的而是引用別人的report 的 所以用了to have 這個形式

    第二種用法是future

     he is to have become the next president by the end of January

   - he will have become the next  與這個意思想象，不過 will 是uncertain    is to have  是certain

     he was to have been next president (在過去的時點上看未來)

還有現在完成式和過去完成式的用法簡單地補充一下

大家都知道現在完成式是跟time 有關，time 對是用現在完成式還是用一般過去式的一個基準。如果有明確的時間或標志詞例如，since 等比較好判斷，但句子里沒有明顯的提示時應該怎么判斷呢？另外的一半的判斷基準是作者是否對他所表達的東西的態度 – 是一般的陳述還是強調。 如果是一般的陳述那就用一般過去時，如果作者對描述的東西的態度是強調那就用現在完成式 FOR EXAMPLE

     I didn’t eat lunch. I am not hungry  只是一般的陳述

     I haven’t eaten lunch, so I am hungry 這里的前面的部分時后面句子的原因，為了表達后面的這個結果必須強調沒有吃午飯的這件事情。

GMAT的現在完成式大多符合這個規律

如果那位朋友對現在完成是和一般過去式不太好把握的時候，哪這個基準去判斷一下，基本上都很清楚。

一個小tip ：  在打開大全后（word 版面）點擊上面 編輯  - 查找  然后輸入關鍵詞 have 就可以不費力氣找到所有的根現在完成時有關的題了，復習的時候有效地用這個 查找功能 有很大的幫助，可以讓你很輕松地找到某一個類型來復習。例如 復習比較就可以輸入  than , as, rather than 等 。

過去完成式是從根本上說就是在過去的時點上用一般現在時，也就是把現在完成時搬到過去的時點了

舉例 大全332題

His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

(A) in which great ice sheets had existed in now currently temperate areas

(B) in which great ice sheets existed in what are now temperate areas

(C) when great ice sheets existed where there were areas now temperate

(D) when great ice sheets had existed in current temperate areas（B）

(E) when great ice sheets existed in areas now that are temperate

我記得很多老師講過去完成式的時候說這個時態用在一個過去的事情發生在另一個過去的事情以前的時候用， 按照此理容易選A 因為

His studies     led    great ice sheets had existed 

這里的led 和 1837 表明 這個propose 發生在過去（只不過這里因為式不定式的緣故看不大出來）

那么 ice sheets existed 是這個以前的事情 是否也應該用had existed 呢

然而，按照上面的我提過的方法 - 過去的時點上用一般現在時 – 來看如果我們假設我們在1837年的時點上看這個問題那么就會是

Agassiz propose the concept of an age in which great ice sheets existed in now currently temperate area  因為這里是一個對ice sheets存在的一般陳述，而不是強調，所以不必要用

have existed  如果是 have existed的話，那么回到現在的時點看的時候 就應該是

led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.

而因為就用過去的時點看正確的也是 sheets existed 所以回到現在也是用一般過去時

可能有點羅嗦，總而言之一句話，也就是把現在完成時搬到過去的時點了。其實從另外一個角度也可以理解- 陳述的兩件事情沒有直接的聯系就沒有什么內在聯系 如 強調等 ，那么也沒有必要用過去完成式了

例外：大全99

 1.   Although the manager agreed to a more flexible work schedule, he said that it must be posted on the bulletin board so that both management and labor will know what everyone is assigned to do.

(A) he said that it must be posted on the bulletin board so that both management and labor will know what everyone is

(B) he said it had to be posted on the bulletin board so that both management and labor knows what everyone is

(C) he said that they would have to post the assignments on the bulletin board so that management and labor knew what everyone was

(D) he said that the schedule would have to be posted on the bulletin board so that both management and labor would know what everyone was（A）

(E) saying that the schedule had to be posted on the bulletin board so that both management and labor would know what everyone had been

said that  后面不用按照indirect speech的規律 盡管said 是過去式，但后面可以跟現在時 我想可能是原話引用的意思吧  我記得還有一道類似的題。