不定式是动词的一种非谓语形式。它可以在句中充当多种成分，其中之一是作定语，放在所修饰的词后面，但应如何确定不定式的语态呢？是to do还是to be done? 这一直是学习语法的一个难点。本文将从逻辑和语义理据出发，对不定式作定语时表主动与被动的区别进行探究。
1. 不定式作定语只能用主动式的情形
1.1 不定式所修饰的名词和不定式中的动词所表示动作是逻辑上的主谓关系（此时，该不定式短语可以转化为一个定语从句），例如：
1）Li Xuemei was the first athlete to get to the finishing line (= …the first athlete who got to the finishing line) (李雪梅是第一个到达终点的选手)。
2）We need someone to help to repair the computer(…someone who will help to repair the computer) (我们需要一个能帮我们修电脑的人)
3 ）He is always the first to bear hardships (=…the first who will bear hardships) and the last to enjoy comforts(=…the last who will enjoy comforts)(他总是一个吃苦在前，享乐在后的人)。
1.2 不定式与它修饰的名词是逻辑上的动宾关系，且主语是不定式中的动词所表示动作的逻辑主语或在句子中能找到其逻辑主语。例如：
1）He has a lot of work to do today. (今天他有大量的活要干。)
2）Do you have anything more to say? (你还有什么要说的吗？)
3）Our teacher arranged us six exercises to do at home. (老师给我们安排了六道练习题在家里做。) (us是to do的逻辑主语)
4）Father always bought his son some toys to play with after his business.（父亲每次出差回来都给他的儿子买玩具玩儿。）(son是to play with的逻辑主语)
1.3 有些句子中，尽管行文上没有不定式的逻辑主语，但是从句意角度可以体会出不定式中隐含着“for sb to do”结构。此时，不定式应该用主动式。例如：
1）There is nothing (for us) to worry about.没有什么可值得担忧的。
2）That will be the only thing (for us) to do now.这恐怕是目前(我们)唯一可行的办法。
3）It is a good opportunity (for us/them) to learn from the farmers.这可是一个向农民学习的大好机会。
1.4 部分形容词，如eager，anxious，determined，able等，其后常跟不定式，它们的同源名词后要用不定式的主动式作定语。例如：
1） (Mr.Smith was eager to get back to teach at the school.)
Mr.Smith"s eagerness to get back to teach at the school was quite obvious.（史密斯先生急于回校教学这一点是显而易见的。）
2） (He was anxious to know the results of the test.)
We could see his anxiety to know the results of the test.（我们看得出他很想知道这次测验的结果。）
3） (They were determined to catch up with us.)
In their speech they expressed their determination to catch up with us.（他们在讲话中表达了他们要赶上我们的决心。）
1.5 部分动词，如attempt，promise，plan， intend，refuse等，其后常跟不定式作其宾语，它们的同源名词后要用不定式的主动式作定语。例如：
1）(They attempted to reach there before five o"clock.)
They failed in their attempt to reach there before five o"clock.（他们试图在五点以前赶到那里，但是没有办到。）
2） (You promised to give me a present on my birthday.)
You haven"t kept your promise to give me a present on my birthday.（你没有遵守在我生日时给我礼物的诺言。）
3） (They are planning to be in business on National Day.)
I guess they will make some changes in their plan to be in business on National Day.（我猜他们在国庆节开始营业的计划得做些变动了。）
1.6 在“with/without +宾语+宾语补足语”结构中，若宾语补足语是不定式(作定语)，不定式所表示的动作将要发生，且句子的主语是该动作逻辑上的执行者，此时不定式须用主动式。例如：
1） With a lot of difficult problems to settle，the newly-elected president is having a hard time.
2） With several meetings to attend, he couldn"t go to the Great Wall with us.（由于有几次会议要参加，所以他不能和我们一起去长城了。）
Without two members to come，we"d better not start the meeting.还有两位成员未到，我们最好先别开始开会。
3）Without anything to do，he turned off the lights and went to bed.已无事可做，所以他关灯睡觉了。
2. 不定式作定语只能用被动式的情形
2.1 当不定式的动作与不定式所修饰的名词有动宾关系，且句中又无它的逻辑主语时，不定式常用被动语态（该不定式短语相当于一个含被动语态的定语从句）。例如：
1）Are you going to the meeting to be held (which is to be held) this afternoon? (你打算去参加今天下午举行的会议吗？)
2）The medical team to be sent (which is to be sent) to be flooded-stricken areas will start off next month.(派往洪灾地区的医疗队下个月即将启程。)
2.2 为了表达需要，强调不定式动作的执行者时，须用被动式，常用by结构引导。例如：
1） 2008 Olympic Games is the first great Olympic Games to be held by Chinese. 2008年奥运会是中国人首次举办的奥运盛会。
2.3 不定式所修饰的名词是将要被做的事情时，不定式须用被动式。例如：
1）The problem to be discussed at the next meeting is of great importance.下次会议上将要讨论的这个问题至关重要。
2）The building to be built next year will be used as the office building.明年要建设的大楼将用作办公楼。
注意：在“There be”结构中，主语被不定式修饰(不定式作定语)时，既可用主动式，也可用被动式，意义上无甚区别。例如：
1）There was a lot of problems to deal with/to be dealt with.有许多问题需要处理。
2）There are three experiments to do/to be done. 有三个实验要做。
3）There is nothing to fear/to be feared. 没有什么可怕的。
巩固练习：
1）He is not a man ____(bow) before difficulties.
2） They had no chance for them ____(go) abroad in those years.
3）You should have confidence in your ability ____(finish) the task ahead of time.
4） Does he have the intention ____ (attend) Mary’s wedding party with us?
5）This will be one of the greatest bridges ____ (build) by our company this year.
6) There is no farmland ____ (lose) .
