What is the difference in meaning between "As we have seen" and "As we saw" when occured in a book in the following context:
As we have seen/saw, [a description of a phenomenon that occured earlier in the book] (for example, "As we have seen/saw, method X is faster than method Y" or "As we have seen/saw, application X allows you to send encrypted messages to your friends")
Best Answer
As is often the case with choice of tenses in English, both are possible, and reflect a choice the speaker/writer is making in how to structure events in time: there is usually no objective difference.
With "as we have seen" the writer is choosing to relate the previous exposition to the present. This might be for various reasons: for example, it might be very recent in the book; they might be further developing an argument from the section they are referring to.
With "as we saw", the writer is choosing to treat the previous exposition as a finished event.