解析虛擬語氣中動詞的虛擬形式
英語中虛擬語氣的用法很多。在英語教學的過程中，我們常常發現有些學生對各種虛擬語氣結構中的動詞是用現在虛擬式還是過去虛擬式分辨不清，下面我就這個問題作一一說明。
1．表示有可能實現的意願的虛擬結構中，動詞常用現在虛擬式：
（1）it is + adj + that +sb + do/be + sth
該結構中的主語從句表示說話人的意願或主觀態度，結構中的形容詞用來表現說者的意願趨向, 從句中的動詞應用現在虛擬式。可用於該結構中的形容詞包括 advisable, appropriate, crucial, desirable, essential, fitting, imperative（必要的）, important, impossible, natural, necessary, obligatory（必須）, preferable（更好的）, proper, sad, strange, surprising, vital（至關重要的）等。
it was important that she have confidence in herself.
（2） s1 + v + that s2 + do sth
在帶有賓語從句的英語句子中，如主句中的謂語動詞表示以下有可能實現的意願時，從句中的動詞應用現在虛擬式：
<1> 要求: ask, beg, demand, insist, request, require,
<2> 建議: advise, advocate, propose, recommend, suggest
<4> 願望: desire, expect, prefer（寧願）。
<5> 決定：decide。
如：he insisted that you be on time.
it is desired that we get everything ready by tonight.
the commanding officer decided that no one be admitted without a special pass.
（3）n+***…*** that +sb +do sth
表示要求、建議、命令、願望、決定等意義的名詞後如有其同位語從句或表語從句時，這類從句中的動詞應用現在虛擬式。適用於該句型的名詞有advice, conviction, decision, decree, demand, idea, motion, necessity, order, plan, preference, proposal, recommendation, requirement, resolution ***決議***, suggestion, wish。
如：my idea is that we go right now.
the resolution that women be allowed to vote was carried.
（4）fear/be afraid/worried lest sb do sth 表示害怕***擔心***某種可能出現的情況，從句中的動詞應用現在虛擬式。
如: i fear lest he arrive too late.
we were afraid lest it be stolen.
he was at once worried lest she leave him.
2．在用來表示不太可能實現的意願或假設的虛擬結構中，動詞常用過去虛擬式：
（1）would that sb did sth/ had done sth
該結構表示與現實相反的願望（would充當及物動詞），that從句中的動詞應用過去虛擬式。
如：would that i were a student again.
would that you didn’t refuse my proposal of marriage（求婚）.
would that i had told him the change last friday.
（2）if only
if only有兩種主要用法:
① 表示目前較難實現的願望或與過去事實相反的願望。表示目前較難實現的願望時使
if only sb+ did/were sth 或 if only sb could/would do/be sth的結構；表示與過去事實相反的願望時使用if only sb had done/been sth 或 if only sb could have done sth的結構。
如：oh, if he could only come
if only you would listen to reason.
if only i could have gone to the movies.
if only you hadn’t told linda what i said.
② if only 還可帶一個條件狀語從句，該條件句表示一種較難兌現的條件。
如：if only you would help me type my paper this afternoon, i would not have to burn the midnight oil.
if only they were here now, we would be able to discuss the issue together.
（3）but for和except for（若非）
but for 和except for均需置於句首，其後均可接名詞短語，表示與事實相反的假設或條件，其後句子中的謂語要用should/would/could ***not***do/be…來表示對現在的虛擬；而用should/would ***not*** have done/been… 來表示對過去的虛擬。
如：but/except for air and water, nothing could live in the earth.
1．表示有可能實現的意願的虛擬結構中，動詞常用現在虛擬式：
（1）it is + adj + that +sb + do/be + sth
該結構中的主語從句表示說話人的意願或主觀態度，結構中的形容詞用來表現說者的意願趨向, 從句中的動詞應用現在虛擬式。可用於該結構中的形容詞包括 advisable, appropriate, crucial, desirable, essential, fitting, imperative（必要的）, important, impossible, natural, necessary, obligatory（必須）, preferable（更好的）, proper, sad, strange, surprising, vital（至關重要的）等。
it was important that she have confidence in herself.
（2） s1 + v + that s2 + do sth
在帶有賓語從句的英語句子中，如主句中的謂語動詞表示以下有可能實現的意願時，從句中的動詞應用現在虛擬式：
<1> 要求: ask, beg, demand, insist, request, require,
<2> 建議: advise, advocate, propose, recommend, suggest
<4> 願望: desire, expect, prefer（寧願）。
<5> 決定：decide。
如：he insisted that you be on time.
it is desired that we get everything ready by tonight.
the commanding officer decided that no one be admitted without a special pass.
（3）n+***…*** that +sb +do sth
表示要求、建議、命令、願望、決定等意義的名詞後如有其同位語從句或表語從句時，這類從句中的動詞應用現在虛擬式。適用於該句型的名詞有advice, conviction, decision, decree, demand, idea, motion, necessity, order, plan, preference, proposal, recommendation, requirement, resolution ***決議***, suggestion, wish。
如：my idea is that we go right now.
the resolution that women be allowed to vote was carried.
（4）fear/be afraid/worried lest sb do sth 表示害怕***擔心***某種可能出現的情況，從句中的動詞應用現在虛擬式。
如: i fear lest he arrive too late.
we were afraid lest it be stolen.
he was at once worried lest she leave him.
2．在用來表示不太可能實現的意願或假設的虛擬結構中，動詞常用過去虛擬式：
（1）would that sb did sth/ had done sth
該結構表示與現實相反的願望（would充當及物動詞），that從句中的動詞應用過去虛擬式。
如：would that i were a student again.
would that you didn’t refuse my proposal of marriage（求婚）.
would that i had told him the change last friday.
（2）if only
if only有兩種主要用法:
① 表示目前較難實現的願望或與過去事實相反的願望。表示目前較難實現的願望時使
if only sb+ did/were sth 或 if only sb could/would do/be sth的結構；表示與過去事實相反的願望時使用if only sb had done/been sth 或 if only sb could have done sth的結構。
如：oh, if he could only come
if only you would listen to reason.
if only i could have gone to the movies.
if only you hadn’t told linda what i said.
② if only 還可帶一個條件狀語從句，該條件句表示一種較難兌現的條件。
如：if only you would help me type my paper this afternoon, i would not have to burn the midnight oil.
if only they were here now, we would be able to discuss the issue together.
（3）but for和except for（若非）
but for 和except for均需置於句首，其後均可接名詞短語，表示與事實相反的假設或條件，其後句子中的謂語要用should/would/could ***not***do/be…來表示對現在的虛擬；而用should/would ***not*** have done/been… 來表示對過去的虛擬。
如：but/except for air and water, nothing could live in the earth.