The past of can

Budi tried to teach himself IELTS but made no progress. Then he discovered GuruEAP and last Saturday he could achieve band 7.0.

Ok,ok.. I made this one up. It may look like shameless self-promotion, but it's a problem I often see in student writing. Honest.

Consider this scenario:

When GuruEAP first arrived in Indonesia he could speak only English and French. Now, after 27 years in Indonesia, he can speak Indonesian fluently. Last weekend he bought some bananas from the local market and he was able to negotiate a reasonable price.

Here there are two kinds of ability:

  1. A permanent ability that existed/exists continuously over time ("..he could speak../..he can speak.."). Note that this can be past or present.
  2. A temporary ability in the past that existed momentarily, relating to a particular event ("..he was able to negotiate.."). Note that this is always past.

So if we return to the original problem:

Budi tried to teach himself IELTS but made no progress. Then he discovered GuruEAP and last Saturday he was able to achieve band 7.0.

Note that the temporary ability was required in a situation that was difficult and required effort or even struggle.

After a struggle, she was able to upright herself and swim to shore.

All of the other workers left the project, but I was able to complete it by myself.

Despite the pandemic, the business was able to continue operating.

Unfortunately, nobody was able to help.

When she saw Tom with another woman, Kelly was unable to hide her disappointment.