From Twitter:
答えは？Fill in:
The book __ is on the table, __ was written by Sam Harris, is excellent.
a. what
b. that
c. which
Answer:
The solution is to add that first and which second:
The book _that_ is on the table, _which_ was written by Sam Harris, is excellent.
Explanation:
Generally, that defines and which describes. This means that what follows that is essential to the completion of the idea and defines the subject; what follows which is extra information describing the subject and not necessary to the main idea.
That
1. In the sentence above, that tells us exactly book the speaker is talking about: the one on the table. This information is essential, because other books are probably in the room or being considered. So it’s not merely ‘the book’; it’s “the book on the table“. That is the full “name” of this book for the purposes of the sentence.
2. Also in the sentence above, notice there is no comma after that.
Which
3. In the sentence above, which refers back to the subject: the book on the table with extra information about it: that it was written by Sam Harris. This is extra information to add for interest or detail, but it is not necessary for explaining what the speaker has to say–namely that there is a book on the table and that it is excellent. It’s like saying:
The Martian, which was written by a technician and non-professional writer, was a blockbuster movie.
The point is The Martian was a blockbuster; that it was written by a technician, though very interesting, is not the point.
4. Which clauses containing additional information are enclosed by comas. Think of what is in there (between the comas) as words that could easily go inside parentheses:
The book that is on the table (which was written by Sam Harris) is excellent.
The Martian (which was written by a technician and non-professional writer) was a blockbuster movie.
5. That clauses adding essential and defining information to the subject are not enclosed in commas and so could not be enclosed in parentheses.
The book that is on the table is excellent. (there is no place for commas!)
6. Finally, just remember: If you are thinking about adding information to a sentence about the subject, but you could leave that information out without losing the main meaning (of the main clause/the independent clause/the main idea) use which. If you cannot, use that.
Link: http://samharris.org
