Perfect Tense : Only when necessary

[abhishek.shanker]

Wrong: Joe learned about an epoch in which dinosaurs had walked the earth.

Correct: Joe learned about an epoch in which dinosaurs walked the earth.

Explanation: Use Past perfect tense only if the earlier action has a direct bearing on the context of the later action. In the above case learning does not has any impact on dinosaurs walked.

Unable to understand this concept. Is this applicable always? How do we decide if an action has impact on other.

[tim]

i know of no such rule. Past perfect is used to point to a different time period than the one being referenced. It is unnecessary in this sentence because the word "epoch" defines the time period in which dinosaurs existed. Change "epoch" to "country" and you need the past perfect, because otherwise it sounds like dinosaurs existed at the same time as he learned about them..