I happened to hear and read the expression “to be fair” multiple times in a single afternoon recently, so that inspired me to write a short email today about it.
Remember that, even though fixed expressions are fixed phrases with specific meanings that have to be learned and used as they are, they are still structurally and functionally parts of sentences, and, as such, we have to understand their structural and functional roles systematically in order to express meaning with them accurately.
The expression “to be fair” expresses the meaning of “if I am being fair (about the situation that I am talking about or going to talk about)” -- it is an expression that helps to make a statement more balanced or less one-sided.
Usually, we add it to what we are saying/writing after making a negative or critical comment about the topic or situation to acknowledge that there is objectively another side to it, and that it would be “unfair” to see the situation as all bad.
A simple example:
The restaurant was really expensive, but, to be fair, the food was excellent.
這間餐廳真的很貴，但公平一點講，食物真的非常好。
In this context, the speaker first makes the negative comment that “the restaurant was really expensive” -- by then adding “to be fair” in the next part of the sentence, he/she “balances out” the comment a bit by acknowledging that the food was actually very good, so there is a “reason” for it to be “expensive,” even though the main comment is a negative one about the price.
“To be fair” is an expression that allows us to “signal” that we are trying to give a “fairer” or more “balanced” view of a situation even though our main comment is negative or critical.
In a conversation, it can also be that one person says something negative about a situation, and the other person introduces something more “balanced” or contrary to that negative opinion with “to be fair.” For example:
A: The restaurant was so expensive.
B: To be fair, though, the food was excellent.
The meaning expressed by “to be fair” is the same -- it allows us to introduce a more “balanced” view to a negative comment, even when it is one from another person.
So, what is the structural and functional role of the expression “to be fair” in a sentence?
If you have taken our foundational course, you would know that it is a type of modifier phrase called an infinitive phrase -- a phrase that starts with an infinitive form of a verb (like “be” here) marked by the marker “to” and plays the role of a modifier (adverb or adjective) in a sentence.
For example:
To be fair, the food was excellent.
In this one-clause sentence, the infinitive phrase “to be fair” is playing the role of an adverb phrase modifying the core action of the entire clause, that is, “the food was excellent” -- adding a “balancing” qualification to the entire action of this clause.
As an adverb phrase modifying the whole clause, “to be fair” would originally be at the end of the clause. However, as you know from “Core Concepts of English” and elsewhere in my teaching, adverb phrases modifying the whole clause also have the flexibility to move forward to other positions in the clause -- most often to the “topicalized” position at the front.
Because “to be fair” “qualifies” a criticism, it is more often than not “topicalized” to the front of the clause it is modifying -- so that the speaker can “signal” to the listener right from the start that he/she is about to say something more balanced to soften the negative comment.
Recall that infinitive phrases as modifiers (unless they are required by specific verbs) express the meaning of “intended actions” or “actions not yet done,” so, if you apply this understanding to “to be fair,” you can see why it means “if we are going to be fair/if we want to be fair.”
One interesting thing to note is that the “doer” of the action in an infinitive phrase modifier is usually the subject of the entire clause (although it can also be the object or a noun specifically added within the infinitive phrase as well).
For example:
I went to the conference to learn more. /
To learn more, I went to the conference.
（我）為了學更多東西，我參加了那個研討會。
In this clause, the “doer” of the action in the infinitive phrase “to learn more” is implied to be the subject of the entire clause, “I,” also.
However:
To be fair, the food was excellent.
公平一點講，食物真的非常好。
Because “to be fair” is a fixed expression with its fixed meaning of “balancing” a negative comment, it is understood that the implied “doer” of the action in “to be fair” is the speaker rather than the subject or other elements in the clause it is modifying -- here, clearly, the “person being fair” is the speaker.
我最近在同一個下午，多次聽到和讀到「to be fair」這個 expression，所以今天就想寫一封短 email 跟大家講一下它。
記得，即使 fixed expressions 是有固定意思、需要整個學習和記的，但它們在結構和功能上仍然是句子文法的一部分。因此，我們仍然需要有系統地理解它們在結構和功能上的角色，才能準確地以它們去表達意思。
「To be fair」這個表達方式所表達的意思大概是「如果我對我正在講／即將講的情況作出公平判斷的話」——它會幫助我們令一個陳述聽起來更加平衡、沒有那麼片面。
通常，我們會在對眼前的話題或情況作出負面或批判性的評論之後加入這個表達，去承認客觀上這件事也有另一面，而如果將整個情況看成完全負面的話，其實是「不公平」的。
一個簡單例子：
The restaurant was really expensive, but, to be fair, the food was excellent.
這間餐廳真的很貴，但公平一點講，食物真的非常好。
在這個語境中，說話者首先作出「the restaurant was really expensive」這個負面評論——然後在句子的下一部分（「but」連接的子句）加入「to be fair」，就稍微「平衡」了這個評論，承認食物其實非常好，所以即使主要評論是關於價錢貴評論，這間餐廳「貴」也有某個合理理由。
「To be fair」是一個讓我們表示自己正在嘗試對某個情況作出更加「公平」或者更加「平衡」的描述的 expression，即使我們的主要評論是負面或者批判性的。
在對話中，也可以是一個人先對某個情況作出負面評論，而另一個人再用「to be fair」引入一個比較「平衡」或者跟這個負面意見相反的點。例如：
A: The restaurant was so expensive.
B: To be fair, the food was excellent.
「To be fair」所表達的意思是一樣的——它讓我們在一個負面評論之後，引入一個比較「平衡」的看法，即使這個負面評論是來自另一個人的。
那麼，「to be fair」這個表達在句子入面的結構和功能角色是甚麼呢？
如果你上過我們的基礎課程，你會知道它是一種叫做基本動詞組（infinitive phrase）的修飾語詞組——也就是一個由被標記字「to」標示的基本動詞字形開始的詞組（好像這裡的「be」），並且在句子入扮演當修飾語（副詞或形容詞）的角色。
例如：
To be fair, the food was excellent.
在這個單子句句子入面，基本動詞組「to be fair」擔當的是額外副詞組的角色，修飾整個子句的核心動作，也就是「the food was excellent」——令這個核心動作被理解成一個用來「平衡」前面負面評論的補充說法。
作為一個修飾整個子句的副詞組，「to be fair」原本位置會在子句的末端。不過，正如在《Core Concepts of English》課程以及我其他教學入面解釋過，修飾整個子句的副詞組位置上有彈性，可以移前到那子句入面的其他位置——最常見就是移動到子句最前面的「topicalized」位置。
因為「to be fair」表達的是為一個批評加上說話者為了平衡補充的意思，所以它多數會被「topicalized」到它所修飾的子句最前面——這樣，說話者就可以一開始就向聽者表示，自己接下來要講的是一個比較平衡的說法，並且稍微減輕前面負面評論的力度。
另外，大家回想一下，基本動詞組作為修飾語的時候（除非它們在結構上是要完成某特定動詞的），表達的是「要去／會去做……」的意思。所以，如果你將這個理解套用到「to be fair」身上，就可以看到為甚麼它的意思是對負面陳述加入一層「如果我們要公平的話／如果我們想公平一點的話」的修飾意思。
有一點有趣的地方值得留意，就是基本動詞組修飾語入面那個動作的「實行者」，通常是整個子句的主語（雖然它也可以是賓語，或者是一個在基本動詞組入面特別加入的名詞）。
例如：
I went to the conference to learn more. /
To learn more, I went to the conference.
（我）為了學更多東西，我參加了那個研討會。
在這個子句入面，基本動詞組「to learn more」入面那個動作的「實行者」，被理解成也是整個子句的主語「I」。
不過：
To be fair, the food was excellent.
公平一點講，食物真的非常好。
因為「to be fair」是一個有固定意思、表示「平衡」負面評論的固定表達方式，所以「to be fair」入面那個動作的隱含「實行者」，被理解成是說話者，而不是它所修飾的子句入面的主語或者其他元素——在這裡，明顯地，「作出公平判斷」的人是說話者。