Understanding why two complex clauses are forced to refer to past and future events, respectively

Question

Wang Jing's thesis contains two example sentences with 了 in the dependent clause, one of which has a past interpretation and one has a future interpretation.

A. 我写了信以后，才去了公园。 Woo shiee.le shinn yii.houh, tsair chiuh.le gongyuan. I went to a park after I wrote the letter.

B. 我写了信以后，再去公园。Woo shiee.le shinn yii.houh, tzay chiuh.le gongyuan. I will go to a park after I write the letter.

I'm slightly confused though as to exactly why A only has a past interpretation and B only has a future interpretation. It makes sense to me that the tense-bearing English translations given are the most natural ones, but why are others ruled out?

For example, why can't B mean I was going to the park after I wrote the letter?

Answer 1

The difference is in the natures of 才 and再:

再：事情或行为重复，继续 ： repeat or continue something or some behaviour
再：更，更加 once again

才:
表示只有在某种条件下或由于某种原因、
expresses only under some condition or because of some reason
目的而能怎么样。
(your) intention can come to fruition.
用于后一分句，
used after a main clause,
前一小句常有“只有、必须、要、因为、由于”等词语
(the) first clause will often contain “only, need, must, because, due to” etcetera (such) phrases

This is a time: 我写了信以后

我写了信以后，才去了公园。
A time, a deed
After I wrote the letter, I went to the park.

我写了信以后，再去公园。
A time, an intention
After I write the letter, I will go to the park.

Answer 2

才 and 再 both mean "then", the key difference between sentences A & B is having or does not have 了 after the verbs:

A is in the pattern of ["V1 + 了" + then + "V2 + 了"] - both actions were completed in the past.

• 我写了信以后，才去了公园 - After I wrote the letter, then/afterward I went to the park. (After I did V1 then I did V2)

B is in the pattern of ["V1 + 了" + then + "V2"] - V2 is an action to be taken at/after completion of V1.

• 我写了信以后，再/才去公园 - After I wrote/finish writing the letter, then/afterward I will go to the park. (After I've done V1 then I would/will do V2)

Answer 3

The future tense is implied by the 再, and because the second sentence (我写了信以后，再去公园) is future tense, we cannot add a completion 了 after 去. The 再 here is:

表示动作将在另一动作结束后出现
[My translation:] Indicates the action will occur after another action
_{(Source: Pleco dictionary GF, 现代汉语规范词典)}

or

CC-CEDICT: 再 (zài​) ...then (after sth, and not until then)...

The 再 implies the action is yet to be carried out, and in particular it will be carried out once the letter is written. (The 再 also has connotations of future tense when we compare 再 vs. 又.)

If we delete the 再, we can add the completion 了, which implies it is past tense:

我写了信以后，去了公园。

although normally using many 了s in a sentence is considered poor writing. For the first sentence, the author adds 才, which seem to be because they want to make the meaning the first sentence more similar to the second ("only then..."), and have them differ only in tense.

Here's some examples in the wild:

至少，我会让每个父母得到孩子的书面许可之后，再去公园为他们寻找伴侣。 (source)
[My translation:] At least, I will make the parents get written permission from their children, then go to the park to search for a partner.

老大，陈封雷离开以后去了机场，订了离开燕京的机票！ (source)
[My translation:] Laoda, Chen Fenglei after leaving went to the airport, and booked a ticked away from Yanjing!