In Column 124 I discussed some expressions using "care". In this Column I will look at two more expressions with "care".
The very common expression "couldn't care less about ... / wh-..." entered British English about seventy years ago, and later crossed the Atlantic to the United States, where it is commonly used. The meaning is "I do not care about it at all / what happens at all", as in:
1) I couldn't care less about him / what happens to him.
The expression is always with "could not", never with "cannot". Therefore according to the rules of sequence of tenses you often see examples like this:
2) I couldn't care less what happened to him.
The literal meaning of "I couldn't care less about him" is:
I care about him 0%, therefore it is impossible for me to care about him less than 0%. In other words, I do not care about him at all.
In the United States the negative sometimes is omitted, but with the same meaning:
3) I could care less about him / what happens to him.
This is a usage which is criticised as being substandard English, but is nevertheless becoming increasingly popular -- in the United States at least.
It is also very illogical. If we say "I could care less", it means "I do care 20% (for example), and therefore it is possible for me to care less". In other words, "I could care less" suggests that I do care to some extent. But this is not the meaning with which the expression is used. It always means "I care 0%."
So, my advice is to know about both these usages, but only use the standard form (i.e., "...couldn't care less").
In conclusion, here are some example sentences:
4) I could not care less which team wins.
5) I could not care less about the Olympic Games.
6) Some rich people could not care less about poor people.
7) That man thinks he is important, but I could not care less who he is.
8) I could not care less about the money.
9) I could not care less about the salary, as long as the job is interesting.
10) I could not care less about your opinion.
sequence of tenses：時制の一致
to some extent：ある程度は
as long as ...：...の限りは（条件を表す）